Update global package space for Elegit

[dmusican]

Each class in Elegit should have packages defined with a general namespace standard. Likely org.elegit.... ; find a reference on this and decide how to do properly. It's particularly relevant because we're storing preferences using the Java Preferences API, which places them in a user's common Java preferences space. The nodes it goes in is based on that namespace standard, and we shouldn't improperly clutter a user's preferences.