Support in RT Trainer for multiple entities

[jannisborn]

Is your feature request related to a problem? Please describe. Expand Regression Transformer trainer to support multi-entity discriminations, i.e., support the multientity_cg collator from the RT repo

Describe the solution you'd like Passing additional arguments of this collator as command line arguments

Describe alternatives you've considered Reading the three new parameters from the json, not preferred since other parameters are passed from command line