BaseDAO, execwrapper: do not require _user and

_cfg, but use defaults instead.
Avoid runtime error when generating parameter
list for parsing function
Projects: introduce nested Projects

so that we can reflect group hierachies.
CellService: add bulk mechanism for number of volumes.

also:
- add missing return
- add caching option for getFileServers
  and getDBServers
getNumVolumes: allow usage of uuid directly.
DBManager: minor fixes

- set res to NONE if transaction failed.
- fix Regex for getFromCacheByListElement
OSDFsService: add bulk mechanism to update all volumes

this bypasses the DBManager intentionally, since it
is too slow for that.

OSDCellService.py: harmless change.