expression graph building
variable contraction and null edge elimination
simple one-wire code generation
very simple tuple connection elaboration

(this gets us logic gates)
Merge branch 'master' into digital-elaboration

Conflicts:
	src/main/java/org/manifold/compiler/Main.java
	src/main/java/org/manifold/compiler/front/FunctionTypeValue.java
	src/main/java/org/manifold/compiler/front/TupleTypeValue.java
sync with master
Merge pull request #159 from mtrberzi/digital-elaboration

Digital elaboration