refactor & clean up jbosstools-target-platforms repo

Rename branches as follows:

4.2.0 -> 4.20.x (currently contains 4.20.6)
4.2.1 -> 4.21.x (currently contains 4.21.4)
(new) -> 4.22.x (soon will contain 4.22.0)
4.3.0 -> master (currently contains 4.30.3)

Also, purge any large binaries that are causing the repo to be >50M in size.

When Kepler R is released (Eclipse 4.3.0.Final) we can branch a 4.30.x branch and work on the new 4.31.x target platforms (Kepler SR1) in the master branch.