[v8r6] Fixes in TS plugin and API

• The addAncestors() method in the plugins didn’t take properly into account the case when ancestor (RAW) files had been reset Unused or were already Assigned or Processed. Now, add in tasks only ancestors that have just been added to the transformation.

• Add an LHCb-specific getAccessURL() method in LHCbDirac API (ganga request)

• Allow dirac-dms-get-file to specify source SE

• Add knowledge about new plugin in transformationDebug

• Add parameter ExcludedFileTypes to the MCDSTBroadcast plugin (in order to not replicate histogram files)