no reasong to keep this file under git

it is found by default in the normal MATLAB distribution
take off unnecessary entry into MediatorSpace
creation of TRI6 class

and modification of all relevant files for integration of that new
class. This class should serve as a basis for representation of all
fields: alpha, level-sets, etc ... the fact of using tri6 instead of
tri3 relieves some problems of definition of alpha on triangles.
creation of levelSet class
creation of discontinuous class
modification of plot function name in TRI6
make all routines compatible with the new classes introduced

only in 2D for now