Updated versions of tools/testing scripts for update2

Adding manual testing scripts (originally written by
paulduffin@ for the original update code) with the
necessary changes to make them work with update2.

Difference include:
1) Removing checksum checks - the new format doesn't
do them.
2) Create a "current version" update: it is now allowed
to update with a version that *is the same as* or better
than the version in /system.

Bug: 31008728
Test: Manual
Change-Id: Ib3ca395258cb22ff1dd8e34d7d916cd626819e57