Reenable Editor Plugin.

[CedNaru]

The editor plugin has been disabled since Godot 4 because we didn't have the time to go over it and adapt it to Godot 4.
On top of that, the code was made extremely early when we weren't used to Godot's internal (we only knew the GDNative API before) so we had a lot of aberrations in it.

I removed most of it to keep only the core features:

• Add a button to build the JVM project using gradle. The result of the build is then displayed in a window.
• Automatically build the JVM project when the game is about to be run. It displays a window only in case of build error.
• "About" Dialog, that can optionally be displayed the first time a user open the editor to warn them about the module.

As a new feature, you can also generate the JVM/Gradle project from the editor now.

For that purpose, I directly encoded the files into a header using a python script. The script has been saved so we can use it whenever the template files need to be updated. Note that there is a new version.h to update, it will automatically replace the version used in the template.

[chippmann]

As a question; could that python script not be executed via scons as part of the build?

[CedNaru]

Added template generation directly when building the engine.

[chippmann]

After creating the files from within the godot editor plugin, the gradlew file still needs to be made executable.
We should do this after we created the files