Switchable STS unpacker algos with legacy support for 2020 runs.

Implemented a base class CbmStsUnpackAlgoBase which fits into the new unpacker scheme of @praisig. The unpacker class CbmStsUnpackAlgo now derives from this. Then added the additional derived class CbmStsUnpackAlgoLegacy, which supports the 2020 runs, including monitoring.

The main difference between the recent and the legacy unpacker is the different treatment of the time stamp, and the fact that the old unpacker discards the first time slice of every tsa file. In principle, if it is desired, the FW-binning switch can be reintroduced into the Legacy class. Furthermore, CbmStsUnpackAlgoBase can be used for future versions of the unpacker.

The legacy class has been tested on run 831 and shown to exactly reproduce the results of the 2018 unpacker.

A minor bug fix was applied in CbmStsUnpackConfig: algo->MaskNoisyChannel() is now called after algo->Init() instead of before, which is how it needs to be.

Suggested reviewers: @praisig @p.-a.loizeau @f.uhlig