Audit Log: add audit log calls everywhere needed

[tpurschke]

see roles/lib/files/FWO_Logging/Log.cs WriteAudit method

• [ ] biggest issue: also get admin name into audit log everywhere (userConfig?) - needs some conceptual work

Before going public, add WriteAudit calls where needed:

• [x] login
• [x] logout see here (?) -> check
• [ ] change settings (except for personal UI language)
• [ ] at import - every import attempt (no c#!)
• [ ] new mgmgt
• [ ] every delete action

Other:

• [ ] add user to function call (optional parameter)