Full model interface restructure to functions

(cat:insert obj) becomes (insert 'cat obj), I got over my obsession with
the former.  The macrology was too complex and inflexible for user
defined schemata and sequences.  That's all gone now and the only change
the user will really see is the syntactical one above...

REAMDE.md has been updated and the (very informal) tests should run.
Fix some README typos