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
Selector: add 'setEnabled' control

The control allows to set the array of enabled-flags directly,
for example [0,1,1,0,1,0...];
improve support for realvec arithmetic
marsystems: add Map: map input to output via control flow
realvec: fix compilation without C++11
MarControlValue: separate arithmetic operations from comparison

Some types (like realvec) have well defined arithmetic operations
but not arithmetic comparison.
fix Delta [fixes #32]

This fixes Delta when inSamples == 1, at the cost of removing its
optional functionality that was arguably reaching beyond its domain
anyway.

Building of the MIREX 2009 code that was the sole user of the removed
functionality is also disabled, with a note how to restore the required
functionality.
inspector: restrict compilation of a feature requiring Qt >= 5.2
inspector: control view: auto-resize Name column