Add maven support

Maven is a build system that is commonly used with Bukkit plugins. It allows for open source programs to be easily compiled on various systems without the need of finding jars and importing them as libraries.

I believe this would be a nice edition to mcore, being that it is commonly used across various plugins, and people want development releases to new versions (1.7.8 at the time this is written, there is no current mcore build available unless compiled by the end user)