implemented methods to disable and enable different log types
Added documentation.
Made GetOutputType() method in mbilogBackendBase const.
Changed output type of berryQtPlatformLogModel to "Other".
Extended mitkLogTest to test the new mbilog methods EnableBackend / DisableBackend.
removed macro defines and changed return value of Disable-/EnableBackends to void
Merge branch 'bug-17987-EnableDisableMbiLog'