An initial stub Gtk application.

- Added NuGet references to MfGames.GtkExt and related assemblies.
- Created the basic window with a text editor and a stub.
- Fixed references to C5 across the board.
Work on getting a menu item showing on the screen along with some basic IoC processing stubs.
Added in project loading for the Gtk client.

- Created project event arguments and events for loading and unloading projects.
Initial version of the ProjectLineBuffer which exposes a project's blocks as a line buffer for the text editor.