Issues vol.1

[StefanSidlo]

Implemented solution for isssues:

• Add "new" to model window menu #16 Added button in menu to open new editor window
• Update window title #14 Cmp and Tree windows have titles based on model or file path (if model name is undefined) Editor Windows have generic titles, because models can be imported in them.
• Isolate state of decision tree editor #13 Only one tree editor window can be opened by session
• Figure out which operations need a progress bar and async treatment #12 Made functions that need time async, and used loading animation to freeze UI while waiting for their result
• Manual #10 Added manual to app
• Figure out how to show version number #8 Basic version number is shown in every window
• Consider using system menu for "typical" functionality #6 There is one menu for all windows. Model import/export actions from menu are supported only in model editor window

[daemontus]

There are some minor things I'll make issues for later (e.g. the loading bar is behind the precision bar in the tree editor), but we can definitely merge this now.