Selection, paste and other improvements

Improved language support for similar languages. If languages with different regions are similar enough, they can share a lang file without the region extension and the region specific file can just contain the translations that are different.
Hopefully fixed some more OpenGL issues.
Cleaned up the built release to remove the unused source code.
minecraft:cave_air is now treated like normal air in the 3D editor.
Fixed some issues with the selection being unpredictable.
Improved the paste tool to bring it in line with how it behaved before the recent rewrites.