New, cleaner examples code
Improve docstrings for PP-JSON and OBJ
Simplify system description
Add valid-from/to keys option to HISTORY
Tidy up README and augment TODO
Rename GET FETCH, COUNT TALLY, DELETE ERASE

Now there are no CL reserved symbols in the model interface.
More consistent terminology for model docstrings
Draft versions of user guide and beginner's guide
No need for model package, no more name clashes
Prefer EXCISE to ERASE for what should be DELETE
Ensure no interface function clashes with CL symbol

Of course there is no single right way but this makes the example
code as simple as possible which is a virtue in itself.

Rename simple-2 example just simple.

Tidy up examples given new model interface names.
Add ENSURE-MODEL and ENSURE-BACKEND to interface
Tidy up package exports
Remove ! from drop-model and drop-backend
fixup ensure-backend
Move user query doco to user guide
Add docstrings to JSON syntactic sugar macros
Another package.lisp reorganize
fixup interface.lips docstrings
Docstrings for symbol util functions