Added 'Glass' theme (replaces Frosty in #82)

src/themes/styles/glass/metadata.json

@@ -0,0 +1,10 @@
+{
+  "name": "glass",
+  "title": "Glass",
+  "style": {
+    "window": {
+      "margin": 29,
+      "border": 3
+    }
+  }
+}

src/themes/styles/glass/style.less

@@ -0,0 +1,70 @@
+@import "../../../stylesheets/theme.less";
+
+@base_background_color        : #fefefe;
+@base_foreground_color        : #656565;
+@gui_border_color             : #c3c3c3;
+
+@gui_input_border_color       : #c3c3c3;
+
+application-window-buttons > .application-window-button-entry {
+  margin : 2px;
+  width : 10px;
+  height : 18px;
+  padding : 4px;
+  text-align : center;
+}
+
+application-window-content {
+  background : @base_background_color;
+}
+
+application-window:before {
+  top : -30px;
+  left : -5px;
+  right : -5px;
+  bottom : -5px;
+  opacity : .7;
+  border : 1px solid @base_background_color;
+}
+
+application-window-buttons {
+  height : 10px;
+  top : 50%;
+  margin-top : -6px;
+}
+application-window-buttons > .application-window-button-entry {
+  height : 10px;
+  width : 20px;
+  padding : 0;
+}
+
+/* Max */
+application-window-button-maximize,
+application-window-button-maximize:hover,
+application-window-button-maximize:active,
+application-window[data-focused="true"] application-window-button-maximize,
+application-window[data-focused="true"] application-window-button-maximize:hover,
+application-window[data-focused="true"] application-window-button-maximize:active {
+  background : url('glas/wm/maximize.png') no-repeat bottom center;
+}
+
+/* Min */
+application-window-button-minimize,
+application-window-button-minimize:hover,
+application-window-button-minimize:active,
+application-window[data-focused="true"] application-window-button-minimize,
+application-window[data-focused="true"] application-window-button-minimize:hover,
+application-window[data-focused="true"] application-window-button-minimize:active {
+  background : url('glas/wm/minimize.png') no-repeat bottom center;
+}
+
+/* Close */
+application-window-button-close,
+application-window-button-close:hover,
+application-window-button-close:active,
+application-window[data-focused="true"] application-window-button-close,
+application-window[data-focused="true"] application-window-button-close:hover,
+application-window[data-focused="true"] application-window-button-close:active {
+  background : url('glas/wm/close.png') no-repeat bottom center;
+}
+