Gridcoin wallet rebranding and redesign

* replace old gridcoin logo with the new one
* replace some key icons with new ones kindly provided by JoShoeAh
* all new icons/images are in svg format
* introduce a dark color scheme
* revise color schemes in collaboration with JoShoeAh
* make the icons switch with the color scheme
* remove obsolete png images

src/qt/bitcoin.qrc

@@ -1,10 +1,6 @@
 <RCC>
     <qresource prefix="/icons">
-        <file alias="bitcoin">../../share/pixmaps/grcsimple.png</file>
-        <file alias="address-book">res/icons/address-book.png</file>
         <file alias="quit">res/icons/quit.png</file>
-        <file alias="send">res/icons/send.png</file>
-        <file alias="toolbar">../../share/pixmaps/grcsimple.png</file>
         <file alias="connect_0">res/icons/connect0_16.png</file>
         <file alias="connect_1">res/icons/connect1_16.png</file>
         <file alias="connect_2">res/icons/connect2_16.png</file>
@@ -19,25 +15,13 @@
         <file alias="transaction_4">res/icons/clock4.png</file>
         <file alias="transaction_5">res/icons/clock5.png</file>
         <file alias="options">res/icons/configure.png</file>
-        <file alias="receiving_addresses">res/icons/receive.png</file>
         <file alias="editpaste">res/icons/editpaste.png</file>
         <file alias="editcopy">res/icons/editcopy.png</file>
         <file alias="add">res/icons/add.png</file>
-        <file alias="bitcoin_testnet">../../share/pixmaps/grcsimple.png</file>
         <file alias="edit">res/icons/edit.png</file>
-        <file alias="history">res/icons/history.png</file>
-        <file alias="overview">res/icons/overview.png</file>
         <file alias="export">res/icons/export.png</file>
         <file alias="synced">res/icons/synced.png</file>
         <file alias="remove">res/icons/remove.png</file>
-        <file alias="tx_mined">res/icons/tx_mined.png</file>
-        <file alias="tx_cpumined">res/icons/tx_cpumined.png</file>
-        <file alias="cpumined_blue">res/icons/cpumined_blue.png</file>
-        <file alias="tx_input">res/icons/tx_input.png</file>
-        <file alias="tx_output">res/icons/tx_output.png</file>
-        <file alias="tx_inout">res/icons/tx_inout.png</file>
-        <file alias="lock_closed">res/icons/lock_closed.png</file>
-        <file alias="lock_open">res/icons/lock_open.png</file>
         <file alias="key">res/icons/key.png</file>
         <file alias="filesave">res/icons/filesave.png</file>
         <file alias="qrcode">res/icons/qrcode.png</file>
@@ -47,17 +31,45 @@
         <file alias="block">res/icons/block.png</file>
         <file alias="ex">res/icons/ex.png</file>
         <file alias="www">res/icons/www.png</file>
-        <file alias="boinc">res/icons/boinc.png</file>
-        <file alias="gold_cpumined">res/icons/gold_cpumined.png</file>
         <file alias="chat">res/icons/chat.png</file>
-        <file alias="voting">res/icons/voting.png</file>
+        <file alias="tx_inout">res/icons/tx_inout.svg</file>
+        <file alias="tx_input">res/icons/tx_input.svg</file>
+        <file alias="tx_mined">res/icons/tx_mined.svg</file>
+        <file alias="tx_output">res/icons/tx_output.svg</file>
+        <file alias="tx_cpumined">res/icons/tx_por.svg</file>
+        <file alias="overview_native">res/icons/icons_native/overview.svg</file>
+        <file alias="overview_light">res/icons/icons_light/overview.svg</file>
+        <file alias="overview_dark">res/icons/icons_dark/overview.svg</file>
+        <file alias="voting_native">res/icons/icons_native/Voting.svg</file>
+        <file alias="address-book_native">res/icons/icons_native/address-book.svg</file>
+        <file alias="lock_closed_native">res/icons/icons_native/lock_closed.svg</file>
+        <file alias="lock_open_native">res/icons/icons_native/lock_open.svg</file>
+        <file alias="receiving_addresses_native">res/icons/icons_native/receive.svg</file>
+        <file alias="send_native">res/icons/icons_native/send.svg</file>
+        <file alias="voting_light">res/icons/icons_light/Voting.svg</file>
+        <file alias="address-book_light">res/icons/icons_light/address-book.svg</file>
+        <file alias="lock_closed_light">res/icons/icons_light/lock_closed.svg</file>
+        <file alias="lock_open_light">res/icons/icons_light/lock_open.svg</file>
+        <file alias="receiving_addresses_light">res/icons/icons_light/receive.svg</file>
+        <file alias="send_light">res/icons/icons_light/send.svg</file>
+        <file alias="voting_dark">res/icons/icons_dark/Voting.svg</file>
+        <file alias="address-book_dark">res/icons/icons_dark/address-book.svg</file>
+        <file alias="lock_closed_dark">res/icons/icons_dark/lock_closed.svg</file>
+        <file alias="lock_open_dark">res/icons/icons_dark/lock_open.svg</file>
+        <file alias="receiving_addresses_dark">res/icons/icons_dark/receive.svg</file>
+        <file alias="send_dark">res/icons/icons_dark/send.svg</file>
+        <file alias="history_dark">res/icons/icons_dark/transactions.svg</file>
+        <file alias="history_light">res/icons/icons_light/transactions.svg</file>
+        <file alias="history_native">res/icons/icons_native/transactions.svg</file>
     </qresource>
     <qresource prefix="/images">
-        <file alias="about">res/images/about.png</file>
         <file alias="splash">res/images/splash3.png</file>
-        <file alias="bkg">res/images/bkg.png</file>
-        <file alias="logo_hz">res/images/gridcoin_horizontal.png</file>
         <file alias="boinc">res/images/boinc_logo.svg</file>
+        <file alias="about">res/images/about.svg</file>
+        <file alias="logo_hz">res/images/gridcoin_horizontal.svg</file>
+        <file alias="boinc_w">res/images/boinc_logo_white.svg</file>
+        <file alias="gridcoin">res/images/gridcoin.svg</file>
+        <file alias="about_light">res/images/about_light.svg</file>
     </qresource>
     <qresource prefix="/movies">
         <file alias="update_spinner">res/movies/update_spinner.gif</file>
@@ -131,5 +143,6 @@
     <qresource prefix="/stylesheets">
         <file alias="light">res/stylesheets/light_stylesheet.qss</file>
         <file alias="native">res/stylesheets/native_stylesheet.qss</file>
+        <file alias="dark">res/stylesheets/dark_stylesheet.qss</file>
     </qresource>
 </RCC>