Support for skill trainers and level requirements.

Hey everybody,

I just uploaded a new update for the plugin.
You can now open the skill tree in display or edit mode. This can be used with skill trainers. There are now level requirements for nodes and you can enable skill tree updates, so that the skill trees ingame update when you change the Techtrees.json.

I also updated the Tree Builder App to be more user friendly and added a copy paste installer for the plugin. Just paste the contents into your project folder, create your Techtrees.json and enable the plugin.

Best regards,
Felski

Changelog:
v1.3.0
Minor Changes:
- added a new plugin parameter to make the skill tree scene in the menu display only.
- added plugins commands to prepare the TECHTREE command.
  TECHTREE DISPLAYONLY
     opens the tree in display only mode, similar to the new plugin parameter
  TECHTREE PRESELECT [tree uid]
     preselects a specific tree for the actor. If the tree isnt found, the default selection is used.
  TECHTREE SINGLE
     prevents the user from changing trees

- these two changes can be used to make the plugin work with skill trainers.
  Example: 
     Enable the plugin parameter so the skill tree is only for display in the
     menu and then add skill trainers all over the world (use the plugin command
     TECHTREE to open the trees in change mode).

- added a new plugin parameter "Update Skill Trees". With this enabled, the skill trees of saved games will update when you change the Techtrees.json file.
  - actors will properly unlearn skills that you have removed and learn skills you've added. Stat changes will also apply properly. Switches will change accordingly and Evals will run again.
  - Common Events will NOT run again. 
  - this feature is experimental. Any feedback is much appreciated!

- added level requirements to the skill trees. Added the corresponding field to the Tree Builder App. Actors can only unlock the node when they reached the required level.

Tree Builder App
- updated the Tree Builder App, so you can now more easy load and save the JSON.