delay instantiation of primitives until Namer

get it out of TokenMapper.  this is just a small step towards
eventually delaying instantiation until the middle end.
eliminate command/reporter distinction in TokenMapper, tokens.txt
move TokenMapper to compile.front

because it talks about org.nlogo.prim, even if only inside strings
make ExpressionParser less reliant on nvm.Instruction
push handling of ReferenceType forward into middle end

and eliminate _reference prim. this cuts a dependency of compile.front
(ExpressionParser) on nvm (Referenceable) and prim (_reference)
push handling of _unaryminus into compile.middle

since then ExpressionParser doesn't need to know about prim._minus.
(it now recognizes it as special not by an instanceof check, but by
seeing that its syntax is infix and minimumOption is set, to indicate
that the left input is optional)

part of my project of reducing dependencies of ExpressionParser
on engine packages like prim and nvm