Solutions and suffixes pre- / postsolve

[glebbelov]

Propagate solutions and suffixes to / from expression trees and the solver model.

• Implement .FuncPieces and other Gurobi attributes for non-linear functional constraints
• Warn about contradicting suffix values for subexpressions
• Have a default / configurable resolve mechanism
• But only for constraints using that suffix
  • This is necessary because, e.g., Gurobi does not accept FuncPieces attr for other general constraints
• Possibly, API for automatic delivery of such suffixes (no user Pre- / Postsolve code). Done?
• For solutions, take e.g. dual value only for the main constraint of the group
• For multi-objective models with objno, need to present only 1 value in the OBJ suffixes, and recover the whole value vector from 1 value when reporting
  • Decided to do this pre- / postsolve in mp::BasicProblem
  • Added ProblemBuilder::NotifyObjChoice
  • Test reading such a suffix: done in funcpieces_01_01_obj.mod
  • Test writing such a suffix: done only for mipbound_01 bestbound=1 return_mipgap=3 objno=0 and with dietobj... cases with MP2NL/Knitro... TODO also for a multi-obj in a single solver