Win32GUI - v1.6 released

- added docs
- very close to fully abstracting events.
- solved small bugs
- added enumerations - see "Enumerations" in the documentation
- added window_base::minimize & maximize
- when testing, dump all thrown win32gui exceptions/ caught ones as well.
- some statics are registered to be deleted only when ~all_windows are destroyed.
- refactored detail/ directory
- refactored event_handler
- added dialog::dlg_res_id() - returns the ID of the resource the dialog was created from.
- solved bug at comparing signals.