Fix const bug in mCRL2 greybox
Fix const bug in mCRL2 greybox

The group info object only contained a reference (const&) to the model
data coming out of mCRL2. Unfortunately, this model data is allocated
on the stack (l.322). Hence, after the MCRl2loadGreyboxModel function
has retured we essentailly have a reference to random
garbage.

Solution: replace the reference by an actual copy (let the copy
constructor work it's magic).

alaarman/ltsmin,alaarman/ltsmin,buschko/ltsmin,vbloemen/ltsmin,Meijuh/ltsmin,buschko/ltsmin,thedobs/LTSmin,buschko/ltsmin,vbloemen/ltsmin,utwente-fmt/ltsmin,thedobs/LTSmin,thedobs/LTSmin,trolando/ltsmin,lordqwerty/ltsmin,vbloemen/ltsmin,Sybe/composition,alaarman/ltsmin,vbloemen/ltsmin,Sybe/composition,alaarman/ltsmin,Meijuh/ltsmin,trolando/ltsmin,Meijuh/ltsmin,Meijuh/ltsmin,buschko/ltsmin,utwente-fmt/ltsmin,vbloemen/ltsmin,utwente-fmt/ltsmin,utwente-fmt/ltsmin,lordqwerty/ltsmin,trolando/ltsmin,lordqwerty/ltsmin,Meijuh/ltsmin,trolando/ltsmin,Meijuh/ltsmin,Sybe/composition,thedobs/LTSmin,lordqwerty/ltsmin,utwente-fmt/ltsmin,alaarman/ltsmin,vbloemen/ltsmin,alaarman/ltsmin,utwente-fmt/ltsmin,Sybe/composition,vbloemen/ltsmin