Refactors ControlNode::getConsumers()

Function now returns boolean value which is true when
at least one consumer was found. Consumer list is
returned via out parameter.

Issue: #32
Refactors graph optimizer by using ControlNode::getConsumers()

Issue: #32
Removes value stack methods, replaces popValue() with getArument()

Issue: #32
Reverts push instructions to simple holder style

Issue: #32
Removes TDeferredValue and TSimpleValue

Issue: #32
Removes unused referer and stack values junk

Issue: #32
Adds missing node values

Issue: #32