GTK+3 Port

This is largely the same as v0.4 now based on the GTK+3 port by @Cimbali

This release contains the following UI changes:

• Estimated Time support: The estimated time can be set by clicking on the label. During the final five minutes the Elapsed Time label fades from white to green. After that and during the next five minutes the color changes to red.
• Add support, via shortcuts, for Logitech presenters (like R400)
• Preview window is optimized for 16:9 screens.
• Text Annotations support: All text annotations of a page are shown as bullet list in the presenter window

Version v0.4

This release contains the following UI changes:

• Estimated Time support: The estimated time can be set by clicking on the label. During the final five minutes the Elapsed Time label fades from white to green. After that and during the next five minutes the color changes to red.
• Add support, via shortcuts, for Logitech presenters (like R400)
• Add option and shortcut (b) to temporarily blank the screen. The "blank color" can be switched between black and white via the menu or shortcut (w).
• Preview window is optimized for 16:9 screens.