Use the same session for drop/create/migrate in cleanMigrate
Check peer schema versions after drop in cleanMigrate.

log.warn if there are peers with different schema versions.

This shall help debug an issue with cleanMigrate where tables were
still existing even after drop/create schema. This happened when
drop/create/migrate schema used different sessions, so perhaps
this is already fixed.
Update to latest datastax java driver
Push version to 1.0.2