Coding style changes
	Use nullptr. Define nullptr for pre-11 builds.
	Use override. Define override for pre-11 builds.
	Convert member m_Variables to _variables, as the latter is the
	    currently prevailing style, while the former one is extinct,
	    and for a good reason, being more difficult to type and see.
	Remove parentheses from returns
	    I was using return(x) syntax for consistency with operators
	    like sizeof(x), which have precedence rules. Return does not
	    have those, being a statement. But the main reason is that
	    in C++14 functions using auto return, "return(x)" returns a
	    deduced reference type while "return x" returns a value type.
	    This can result in returning a reference to a local. See
	    Myers Effective C++ for further discussion.
	Use move on rvalue references and forward on universal references
	    As discussed in "Effective C++", this distinction is made on
	    whether type inference occurs. When forwarding arguments whose
	    types are not inferred, move should be used, not forward.
Fix too short test sequences in array bvt