Allow changing feature profile via EditorInterface

[RedMser]

• Add EditorInterface.set_current_feature_profile(profile_name: String) method to load a feature profile by name.
  • Validate the specified feature profile (ensures the profile file exists).
• Add complementary EditorInterface.get_current_feature_profile() method. This returns a string, but you can easily retrieve the EditorFeatureProfile instance from it (see example project).
• Add documentation hints for how to programmatically register feature profiles.
• Refactor UI code (since the current feature profile is fully determined by the UI...).

This allows creating a plugin or editor script which can automatically generate and/or change feature profiles. Example project here.

[akien-mga]

Looks okay to me, though I haven't tested / reviewed in depth.

[YuriSizov]

Haven't tested either, but aside from a couple of notes the code seems fine. Comments need to be addressed though.

[RedMser]

Here's a simple project for testing the new API: Feature Profiles API Test.zip

It adds menu items in the "Project -> Tools -> Feature Profile" menu, and prints stuff to the Output window. The 3D feature gets toggled by it.

[YuriSizov]

One style change is needed, but otherwise looks fine.

[YuriSizov]

Thanks!