Adapt examples to new ConstrainedSolver API

See merge request !82

remove factored_solver and quadratic_solver examples which overlapped with small_factored_solver and small_quadratic_solver and also accessed private member functions

merge latest changes from ReForm

See merge request !81

# Conflicts:
#	Base
#	CMakeLists.txt
#	NSolver/ConstraintTools.cc
#	Solver/ConstrainedSolver.hh
#	Solver/ConstrainedSolverT_impl.hh
#	Solver/Eigen_Tools.cc
#	Solver/Eigen_Tools.hh
#	cmake-library
#	cmake/FindGMM.cmake

* Clean up, refactor and reformat
* Improve naming and docs
* Simplify the use of the eliminate columns output

* only link Ipopt and OSQP if they are defined targets

* copy some cmake functions from ReForm

* disable some libraries in the config file

* don't use Eigen/SparseExtra due to warning about unsafe scanf

* fix matrix writing in ConstrainedSolver

* remove hardcoded optional dependencies

* add resolve capabilities to SubProblemSolver

* add resolve capabilities to MultiDimConstrainedSolver

* move constraint elimination from ConstrainedSolver into ConstraintTools

* disable GMM related code if GMM is not available

* use Eigen in COMISOSolver

* disable GMM

* remove duplicate fix points in ProblemSubsetMap

* remove EigenLSQConstrainedSolver

* add ProblemSubsetMap and SubProblemSolver

* add solver for constrained mixed integer problems with multiple independent dimensions.