Add .proto files to the editor

[JCash]

It's beneficial for the editor scripts to have the .proto definitions available, in order to correctly load/save files in our file formats.

We could bundle the .proto files in a zip, which is then bundled with the editor, and subsequently unpacked at startup.

Since the files are small, they could be stored as-is as well.

[JustAPotota]

+1

It would also be handy to have a standalone .zip download (like the new defoldsdk_headers.zip package) for all the definition files, that way external tools can use them without having to fetch the 300MB of stuff defoldsdk.zip comes with.