Add the distributed eclipse folder

This folder is distributed with the forge source and required for the
setup in eclipse to work properly.
I also added the .gitattributes file so the line endings for the folder
don't get changed.
This will also prevent strange diffs caused by line endings in the
future.
Update the installation guide

- Add a guide for simply compiling the mod.
- Added instructions for all platforms
- Added instrucions for IntelliJ
- Changed the eclipse instructions to a simpler way.