Coroutines, global #import, Linux...

Additions:

• Added coroutines (wiki) - these can substantially simplify the way sequential code is written.
• A global.gml file can now be added to #import subdirectory for project-wide import rules.
• If you use GMLive, the editor can now show small indicators in resource tree for files which have live reload enabled.
• There's now a pre-packaged x64 Linux build.

Improvements:

• Application menu button now opens a conventional context menu instead of being just a Preferences toggle.
• You can now set/reset normal and open (for folders) custom icons separately, and there's a menu item to open custom CSS file for easier access.
• There are now "expand all" / "collapse all" options in treeview context menus.

Fixes:

• Fixed local variable detection breaking if semicolons are omitted.
• Editor no longer registers a system-wide keyboard shortcut for opening developer tools (Ctrl+Shift+I).
• Obsolete definitions are no longer loaded from API files (as they often lack correct tags/data anyway).
• Fixed backups for objects/timelines denying to open via context menu (files were still intact).
• Folding an event/moment now folds #sections inside of it like it should.