Dark and Light stylesheets fixes/improvements

[pgilfernandez]

• fixed background logo for Win and Linux
• improved QToolBar handle for different icon sizes (selectable by user inside Preferences)
• tweaked editable fields inside QToolBar in order to work for all icon sizes (selectable by user inside Preferences)
• fixed Ubuntu problem that caused a blank line inside up/down buttons of QSpinBox and similar
• tweaked Python Editor color for Light theme
• fixed buttons margin/padding inside Task tab
• tweaked color for checked QPushButtons inside Draft WB for better user experience

[pgilfernandez]

They still lack of the CMake file that I don't know how to create and correctly set...

Thanks

[wwmayer]

Two things to mention:

1. Under Linux there is a problem with the spaces in the qss file names. So, I renamed them.
2. When using any of the style sheets you don't get a visual feedback when the mouse hovers over a tool button or if you click on it.

[pgilfernandez]

1. no problem, I understand it's much better without spaces
2. you are right, it was a design decision based on OSX default theme that behaves the same. I have tried Ubuntu and Windows and they do have this visual feedback so maybe you are right and it's better to include hover and pressed styles over toolbar buttons. I will add them in next update that probably will fix any other issue that is found over this week