Create system user for each new user linked

[wyleung]

In the current setup there is only one user 'ubuntu'.

Ideally, the system should create a linux system-user for each user created by the fedSSH system.

Naming could follow the following scheme:

username: <country>.<institute>.username e.g. nl.lumc.wyleung

or not bound by institute:

username: nl.<username> e.g. nl.wyleung

[wyleung]

Actually this is something already mentioned in the TODO .. about the autoprovisioning. Not something on the account-naming though (also implies setting authorisation / rights etc..)