implement subscriber vty interface, tests

Implement VTY commands for subscriber manipulation:
- create / delete subscriber
- modify MSISDN
- add/edit/remove 2G and 3G authentication data
- show by IMSI, MSISDN or DB ID.
(enable/disable CS/PS and purge/unpurge to follow later.)

Implement VTY unit tests for the new commands using new
osmo_verify_transcript_vty.py from osmo-python-tests.

Depends: libosmocore I1e94f5b0717b947d2a7a7d36bacdf04a75cb3522
         osmo-python-tests Id47331009910e651372b9c9c76e12f2e8964cc2c
Change-Id: I42b3b70a0439a8f2e4964d7cc31e593c1f0d7537
6 files changed