More generic solution for logging into different logfiles
- Log.xyz() method added with additional LogType parameter
- LogType parameter may be any defined log type
- log types are defined in
  - mediaportal\Utils\Services\LogType.cs (for MP client)
  - TVEngine3\TVLibrary/TvLibrary.Interfaces/Logging/Log.cs (for TVServer)
  - Common-MP-TVE3\Common.Utils\Logger\CommonLogType.cs (for log4net framework)
- the log files used for the various log types are configurable in log4net.config