Start the update to Gdk/Gtk 3.

This is a partial update to Gdk/Gtk 3 the gdk sources compile but GtkD
as a whole doesn't compile yet.
GtkDGL was removed since gtkglext depends on gtk 2.x.
Pused the worng demos.
Add Keysyms.d, it's not generated by the wrapper.
glib.DateTime.DateTime.hash should be nothrow.
Remove glade and gtkglext from downloadFiles.sh
Update the paths for Windows and OSX.

The Gtk backend is no longer included in the lib name.
Start the update of gtk to gtk 3.x.
Remove the unused installer files.
Set the correct struct for gtk.CssProvider.
Add A destructor to gtk.SelectionData.
Make sure gtk.StockItem add and addStatic are wraped correctly.
Update the gtk Window an Display Widgets, not a lot of changes here.
Merge branch 'master' of github.com:gtkd-developers/GtkD into Gtk-3.x
Merge Pull request #7 into Gtk-3.x
Add some whitespace to the c function declarations.
Rewrap with the wrapper changes from pull #7.
Update the Gtk Toggle and Button Widgets.
Update the Data Entry and Text widgets.
Update the Tree, List and Grid widgets.
Don't initialize the licence variable in GtkWrapper.d

The licence is read in from APILookup.txt