Add isomorphs comment
Add LitEx protocol
Add LogicEx type for logic-combine
Rename recap to recap-many. Add new recap.
Rename models to parse
Remove nascent defsyntax from seqex.clj
Add Tree protocol for descending a seqex tree
add defrule and better syntax formatting
Fix to (children delay-obj), improve errors

There is something wrong with getting children from delay objects. Made
children do a special check for delay objects. I consider this a stop gap for
now.

Also tried to improve error messages in several ways. I'd like to move towards
implementing error messages in a way that isn't so tightly coupled with the
SeqEx protocol. For example, error messages tailored to syntax macros might be
different from another context.
Add mform. Add let2 example. fix doc bugs.
Improve syntax messages

Also rename vform -> vec-form etc
No longer reify subex. More tweaks to gen docs

Slightly modified let2 example
Add defterminal, add defn2 example, fix doc bug
or -> alt, and -> all, add missing delay, = -> =>