Fix import clause in README
Add *to-json* and *from-json* public specials

Easy for user to bind these at run time.
Doc string improvements for model functions

Document "semi public" convenience utility functions
Remove redundant from-json function

Can just use yason:parse directly
Isolation levels documentation
README interface doc strings reference change
Macroize the make-query defuns

More succinct and now no duplication of symbols