Middle out

[martyall]

• add hash cons sharing for expressions (see Node type in Circuit.Language.Expr)
• drastically simply the compile phase taking advantage of the output of reifyGraph is already (reverse) topologically sorted
• simplify the functions for inputing/returning bools/fields
• add the Unbundled type class
• added partial implementation/test for SHA3 that won't run because something is way too slow.

In addition, I ran the profiler many times to understand where things were slowed down and some adjustments were made:

• Use IntSet and IntMap ubiquitously where possible
• create the InputBindings type to manage labled vars
• add INLINE pragams in a bunch of places