Bump revision for 1.8 release

Update changelog too
Fix init test
Fix annotate text test
Raise limit on ISO (>800 is possible)
Fix split timeout

Unencoded formats were failing apparently due to high start-up costs
Fix failures in the motion array tests

Firmware 707 seems to have fairly major start-up costs when video
recording which meant the tests violated the lower bound in several
instances
Clarify high ISO limits