Instead of having .hsp files that determine which files are members
of a project, a project is now an entire directory tree instead.
This feels a lot less cumbersome to work with, and removes a fair
amount of busywork that would otherwise be expected from the user.
This patch refactors large parts of HackStudio to implement the new
way of thinking. I've probably missed some details here and there,
but generally I think it's pretty OK.
Instead of files disappearing after you switch to something else,
we now keep track of them in a little ListView below the project tree.
You can return to any previously opened file by activating it in the
open files list. :^)
Editors now communicate with the c++ language server when openning and
editing c++ source files, and go through the language server to get
autocomplete suggestions.
Previously, when resolving the paths for the FormEditor widget icons
we didn't take into the account that calling class_name() returns the
widget name with a "GUI::" prefix.
Also, we now skip over widgets that we don't have an icon for.
