Include refactored Flavour Tagging Package into 2018-patches

This is the 2018-patches version of !216 (merged). The commits have been rebased onto 2018-patches and minimal adjustments have been applied (qualifying LHCb enum values where needed, see dba5c787 and 6ac2be67).

Additional MRs to Analysis and Stripping (in parallel to Analysis!317 (merged) and Stripping!763 (merged)) will be opened for 2018-patches in the following days.