Add repopick script from CM

patchset 4: cybojenix
  clean up the script:
    remove fetching from github
    cleaned up fetching locations of binaries
    if ANDROID_BUILD_TOP isn't defined, error out

PS 5:
  Added back the check if fetch succeeded.
  Fixed verbose print about fetching.

patchset 6:
  final changes
    fix detecting ANDROID_BUILD_TOP
    send all relavant data to stderr

Change-Id: If67c5f178d03fadd8b79b1908f4a9cb231efbb28
repopick: Add a way to checkout instead of cherrypick

This helps if you want to take a commit and its dependencies, and not
just a particular commit

Change-Id: Ib245cce560c7b0d6fd03198a8c69a13d4720a4cb