DBS HG1302 updates

Hi Diego,

could you include the following changes to the configuration of dbs and dbsmigration into the HG1302 deployment, please.

Changes:
* Make dbsmigration threads configurable per DB instances
* Use new DBs for default VM deployments, which aren't used by cmsweb
* Disable security for default VM installations, since they are completely independent from cmsweb installations, they use they own DBs and they are only reachable within CERN. 
* New DBs for prod/global on all cmsweb hosts
* Re-enable security for prod/global on cmsweb-dev

Thanks,
Yuyi & Manuel