refactor currentSolver

- change template parameter of solver
- add Solver.def and Solver.hpp to include all Solvers
- add CurrentVillaBune.def and Esirkepov.def to splitt implementation and forward declaration
change currentConfig.unitless

- use new Solver.def and Solver.hpp includes
- update template arguments for solver
Merge pull request #436 from psychocoderHPC/topic-refactorCurrentSolver

refactor current solver