ADD: Arbitrations table
ADD: User groups table
FIX: synchronization for IDCachable-Objects

Move synchronization blocks out so that it's garanteed that only one
instance exists per id.
FIX: do not send "Powered-by"-headers via HTTP
ADD: user group management (with testcase)
FIX: syncing issues for Language initialisation.
UPD: jacoco for testers
UPD: Make all tables UTF8
UPD: [empty] better varname
ADD: jacoco report generation
FIX: paths for resources...
FIX: Some paths in report generation.
ADD: A step towards a more friendly SQL API.
UPD: do PoJam Test with 15