Bug 1065773 - Part 1: Extract Android release signing bits into config/android-common.mk. r=mshal
Bug 1065773 - Part 2: Stop release signing instrumentation test APKs at package time. r=mshal
Bug 1065773 - Part 3: Add release signed instrumentation test APKs to instrumentation/ in tests package. r=mshal
Bug 1065773 - Post: Add release signed Robocop APK to mochitest/ in tests package. r=mshal

This isn't strictly necessary, but if we start fishing these APKs from
the tests package, we can phase out the buildbot and mozharness logic
that handles robocop.apk specially.