This commit is to enable data migrator to support migrates data
from mysql to pgsql, this is a specific step for user to upgrade
harbor across v1.5.0, as we have move harbor DB to pgsql from
1.5.0. It supports both harbor and notary db data migration,
and be split into two steps with dependency.
It also fix issue #4847, add build DB migrator in make process.
Default target version is 1.5.0
This is mainly for VIC-appliance upgrade, and should be considered
experimental for oss due to limited test.
Tested with 1.2 and 1.3 harbor.cfg from VIC appliance.
