Convert Into Gradle, Fix few things

Changes:
Made ComputerCraft and BuildCraft api's optional
Fix pl.asie.lib.chat.Command* (Imported code from 1.7)
Added AccessTransformer for pl.asie.lib.shinonome.EventKeyClient

The name used to signify BuildCraft|Core existence, and the function name for ComputerCraft support, were written by me. If you'd like me to change them or if you want to yourself, feel free.