Update of HP decoders:

Update of HP decoders:

1) Added GetDDLTracker and GetDDLTrigger methods to AliMUONRawStreamTrackerHP
and AliMUONRawStreamTriggerHP respectively to create the DDL payload objects
on the fly. This was done to improve the compatibility of these classes to their
existing counterparts. These methods should however only be used in some rare cases
where one needs the payload object to modify the data and write it back to another
DDL file. Otherwise the existing interface methods of AliMUONRawStreamTrackerHP and
AliMUONRawStreamTriggerHP are much faster.

2) Modified AliMUONDigitMaker and AliMUONReconstruction to handle the new trigger
DDL decoder also. The fast decoders are now enabled by specifying the USEFASTDECODERS
option in the reconstruction options. To make the digit maker use just the fast tracker
DDL decoder use the USEFASTTRKDECODER option. Similarly for just the trigger decoder
you use the USEFASTTRGDECODER option.

Minor fix:
Fixed some documentation in AliMUONVRawStreamTrigger.h

(Artur)