remove count_exp directory

was for proving that the exp and v types are countable. unused facts.
tweaks to top-level README
pull out certain functions into CompilerPrimitivesTheory

That depend on semantics stuff (so are not in CompilerLib), but not on
anything in the compiler itself. Also remove the dependency on the
bigStep and smallStep semantics from the compiler definition (I think
all that was needed is in ast and semanticPrimitives).
move intermediate language definition into separate file
pull out the compiler phase from source to intlang
pull out phase compiling from intlang to bytecode

also, thinking about how much compileTerminationTheory should redefine,
i.e. whether descendent theories should import from the originals or
from it. (or both.)