AnalysisBase Revival, master branch (2019.01.17.)

With this MR I would like to revive a dumbed down version of AnalysisBase in the master branch. The project only builds the xAOD EDM and the standalone I/O code built around it. Its purpose is mainly to allow further developments.

Quite a few files had to be touched, but after updating the files under Project/AnalysisBase the other updates were all just to make it possible to build all core packages needed by AnalysisBase in "standalone mode" once again. This did reveal a number of unfortunate updates in the xAOD packages, which I tried to fix here...

Cc-ing @ksuruliz and @krumnack, they'll probably want to know about this development. Nils, I started updating ROOTCORE definitions to XAOD_STANDALONE in the code, that should be continued later on. I just didn't want to bloat this MR any further with that...

For the shifters: In many files the update goes from 2017 to 2018, because I actually made the commits for those updates still last year. 😛