marsystems: implement FlowToControl

New MarSystem selects a field of the input matrix and outputs it as a
real control value.
MarControlValue: remove useless field 'invalidValue'
MarControlValue: remove useless members tempValue_ and current_link_
MarControlValue: remove useless member lit_
MarControl(Value): remove uselessly duplicated of code
MarControlValue: unify common code among specializations
MarControlValue: support for math with different numeric types
scripting: operation processor: catch invalid-operation exceptions
MarControlValue: improve arithmetic comparison