CurrentSchemaVersion: Allow to use it in plugins

To implement dedicated databases in plugin based on GWTORM, current
version plays important role in upgrading schema version. Change
the modifiers for the attributes and the constructor to allow this.

Gerrit CI plugin needs this to support schema upgrade in init plugin
step.

Change-Id: I372be503cff79a48d1320244e625bc7c5635eca5
1 file changed