Code review comment for lp:~maddevelopers/mg5amcnlo/dim6_eft

The main point for this branch is to do some core change related to the
EFT validation effort (lead by Gauthier/Fabio). This is implemented as a plugin but the accord required some change in the re-weighting module (mainly for the formatting).

Those changes adds:
1) The following command: import process PATH is now supported. (allowing to provide a file with all your process definition whithout any generate/add process
2) Allow the re-weighting to distinguish process based on the process event written in the lhe file / @X [does not seems to work for loop]
3) More xml like formatting for the weight definition (including model version/...)
4) the support for NHEL=-2 in reweighting, which returns the sum over polarization (like -1) but clear all filter associated to the zero-helicity to avoid any possible bias)
5) a (not documented) flag --no_warning=nodiagram which prevent the code to crash if you do not have any diagram generated for a given process
6) possibility to call the reweighting interface as a standalone executable
7) improve the templating of the standalone output to support model with more than 1k parameters (and reduce RAM use for model with less parameters)