Improvements to SelectTemplateDialog (#109 and #142)

- Added side pane for product preview and information
- Product selection is done with a separate pushbutton, so that user gets a
  chance to preview the complete product information before committing to the
  selection
- Supports two view modes: Grid View and List View
- View mode is automatically stored in Settings, so it will default to the
  user's prefered mode
- Should address most concerns in #109 and #142

glabels/icons/flat/22x22/glabels-view-list.svg

@@ -0,0 +1,21 @@
+<svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="22" height="22" >
+
+  <rect x="3" y="3" width="4" height="4"
+     style="fill:#333333;fill-opacity:1;stroke:none" />
+
+  <rect x="3" y="9" width="4" height="4"
+     style="fill:#333333;fill-opacity:1;stroke:none" />
+
+  <rect x="3" y="15" width="4" height="4"
+     style="fill:#333333;fill-opacity:1;stroke:none" />
+
+  <rect x="9" y="4" width="10" height="2"
+     style="fill:#333333;fill-opacity:1;stroke:none" />
+
+  <rect x="9" y="10" width="10" height="2"
+     style="fill:#333333;fill-opacity:1;stroke:none" />
+
+  <rect x="9" y="16" width="10" height="2"
+     style="fill:#333333;fill-opacity:1;stroke:none" />
+
+</svg>