Fogbow integration: VOMS proxy for long living services

Created by: abmargb

Currently there is no renewal mechanism for VOMS proxies implemented in the Fogbow Resource Manager, which might be an issue for long living services such as the OM server. We must come up with a general solution for applications in which the interface with the user won't accept a VOMS proxy, forcing this proxy to be generated and renewed in a different manner. Investigate the concept of robot certificates in the context of VOMS.