Copy the full sample block in the yml for plotIt

What the title says... this was needed by @fbury for "signal" samples (see also https://gitlab.cern.ch/cp3-cms/bamboo/merge_requests/77 ) - then it should also be possible to specify color etc. at the sample level.

The code changes are straightforward, but I may have missed something that should not be copied (in principle both bamboo and plotIt only read the values they need and ignore the rest, but it's hard to know for sure), so I'll wait for someone to check that their plots with nontrivial configuration (data/MC, and signals) still work.

While I was it I added the possibility to specify generated-events as a number instead of recalculating the value from counters (this can be useful in case the latter fails for some reason).