generator: move all request types and functions into request.ml

This avoids the need to autogenerate bits of Makefile, or anything
fancy.

Signed-off-by: David Scott <dave.scott@citrix.com>
Split into two sub-projects

We have a separate project for the code generator, which emits code
which is then linked into the library and CLI.

Signed-off-by: David Scott <dave.scott@citrix.com>