Project UI

[Moneyl]

Port NF project UIs:

• [x] Get file selector + folder selector UIs working. Either use the beef win32 wrapper or the nfd beef wrapper (https://github.com/jazzbre/nativefiledialog-beef). Should recompile myself just in case if the existing library is used.
• [x] Creating new projects
• [x] Opening existing projects
• [x] Closing the current project
• [x] Saving the whole project (Ctrl + S)
• [x] Show unsaved changes confirmation in the following cases and cancel those cases if user clicks cancel:
  • [x] Close project
  • [x] New project
  • [x] Open project
• [x] Don't allow opening maps until a project is open
• [x] Show current project name on the menu bar. If no project is loaded show that.

Recent projects list will be added after #59 since we need a way to make the list persistent. Could throw something basic together with bon but I'd rather wait. Going to need the cvar system anyway for map editor.

[Moneyl]

Completed by 8e36fd90b69d66c4d5bb23945fdcdfbdaeb1f070. Project save/load/create/close will need further testing to make sure state from the previous project gets properly cleared before opening or creating another one. Adding it to #96.