Properties: Superseded PropertyValues by Elementa's States (concept)

[UserTeemu]

A concept implementation for using Elementa's State objects for storing values of properties.

I was inspired to do this PR from improving #25 . The ability to have multiple listeners/actions added in this PR would help getting that other PR ready.

Major changes in this PR:

• PropertyValues are moved into their own file.
• Vigilance's PropertyValues become deprecated.
  • PropertyValue#initialized and PropertyValue#writeDataToFile have been moved to PropertyData
• Actions (that are ran when a value changes) have been internally replaced with State listeners.
  • Major difference is that there can now be multiple listeners. As a consequence, it will no longer allow you to remove one listener by setting another. More about this in a comment.
• Button actions are no longer stored in callable property values. Rather, they are now ordinary value listeners. Listeners are invoked whenever a button is pressed.
• Code of PropertyCollector#getProperty functions have been changed so that there would be less warnings caused by property values being deprecated.
  • Vigilant#registerListener functions were updated to use the PropertyCollector#getProperty function to find PropertyData instances. As a result, Vigilant#registerListener functions can now find more properties (instead of only Java field backed ones) and that code is cleaner.

All feedback is welcome. In the comments, I'll have a few things I especially want feedback on.