VTY: integrate IMEI

Display the IMEI in "subscriber ... show", allow showing and modifying
subscribers by their IMEI with: "subscriber imei ...". For debug
purposes (and to have proper VTY tests), make it possible to change the
IMEI with "subscriber ... update imei".

IMEIs are saved in the database without the 15th checksum number. When
the checksum gets passed, verify it and cut it off.

Related: OS#2541
Depends: I02b54cf01a674a1911c5c897fbec02240f88b521 (libosmocore)
Change-Id: I1af7b573ca2a1cb22497052665012d9c1acf3b30
4 files changed