Begin using gradle

Updated the directory structure and added the necessary files to now use ForgeGradle.
ForgeGradle is how all future versions of forge will be set up. I'm not sure how you even managed to update to 1.7 without it.
While it may be a bit of a change, it is fair easier to work with once you get used to it.
I did a test build and it appears everything is working.

Some notes:
To setup a dev environment, run 'gradlew setupdevworkspace' from a command line/console
To build the mod, run 'gradlew build' from a command line/console
To update the forge version, edit the line in build.properties and run 'gradlew setupdevworkspace' again
Gradle supports lots of different IDEs, so commands like 'gradlew eclipse' or 'gradlew idea' will set up specific things for each IDE respectively


Useful links:
ForgeGradle on the MinecraftForge forums: http://www.minecraftforge.net/forum/index.php/board,118.0.html
Gradle: http://www.gradle.org/
The forge wiki article with some relivant gradle info: http://www.minecraftforge.net/wiki/Installation/Source