Add WWCategorisationProcessor

[ueinhaus]

BEGINRELEASENOTES

• This adds the WWCategorisationProcessor to MarlinReco
• It categorises each event by its WW decays channels. It provides a true category (only meaningful for true WW events) as well as two levels of reconstructed category. They are stored as event parameters.
• This may serve as common coherent categorisation for any analyses using WW events. ENDRELEASENOTES

[Zehvogel]

A couple (optional) suggestions for improvement:

• Add some kind of documentation e.g. a README.md with the expected confusion matrix and the list of samples used to obtain it (and later on link to thesis)
• Truth categorisation can probably be made more robust or simpler by taking the generator status of the particles into account (e.g. 1 is stable -> final state electron)
• usage of the legacy TLorentzVector could be replaced by the "newer" root lorentz vectors

Otherwise LGTM :+1:

[tmadlener]

Merging this now for some further "integrated" testing and to ease developments on top of this.