Separate REPL code from HTM logic, stop forcing autoload, still make autoload convenient

[mrcslws]

Tentative plan:

• Move logic from core.cljx to /comportex/src/org/nfrac/comportex/repl.cljx
• Stop enabling truncation automatically in library code. Require a function call.
• Create /comportex/dev/user.clj. Make it autoload truncation.

This opens the REPL code to other consumers (making user.clj simply a consumer of the API that anyone else can use)