slapproxy: add automatic migration procedure to new schema.

Migration to new database schema is automatically done when an old version is detected.
It keeps the old tables untouched in case of needed rollback to an older version.
slapproxy: move test file to its own module.
slapproxy: give computer reference to partition network.

Also make sure we test adding addresses to partitions.
version up slapos.core 1.2.1