- Feature #569 - #600 - #601 - Support #602: Implement a ReactionDiffusion Model (for that implement a NonLinearSource operator). Currently two are implemented: FitzHugh-Nagumo and MitchellSchaeffer. - Feature #587: Local2Global arrays are now managed entirely at LocalFEltSpace level. Thus some copies are avoided, and it offers better granularity for processor-wise local2global: it is now possible to compute them only for the operators that require them, rather than at the whole Model level. - Support #597: Rearrange RefFElt classes (names were not accurate and comments were not very helpful). - Support #595: Update code to make it work with brand new Petsc 3.6. - Feature #191: Refactor the way Unknowns are handled: Unknown variable is not just a name and a nature; shape functions and unumbering subset are defined in a new class named ExtendedUnknown (which replaces the clumsily named UnknownAndNumberingSubset). Quadrature rules may now be defined specifically for each operator.