Move DefnBase to src/coretypes, make progress with one_line_ify

DefnBase is now home to the updated literal-decider conversion

Make equality of "tight" precedence by default

Start to work through knock-on effects of this.

Add composition thm for SUM_MAP; document sums better in DESCRIPTION

In particular, use polyscripter for the presentation of the core sum
theorems.

Change sum$++ to be sum$SUM_MAP

In places that use the old notation heavily, it is relatively easy to
reinstate it, as happens in quotient_sumScript.sml.

Closes #635

Remove TABs from src

Will also make selftest to check that they aren't introduced

Generate "standard" datatype simpl rewrites as tyinfos are loaded

This saves us from having to write them out to disk, which can make
for unnecessarily large theory.dat files.

Use TypeBase.export to avoid adjoin_to_theory calls

Still need to use the same facility in the implementation of Datatype.

Move smpp to Portable - get everything up to arithmeticScript working

Rename TypeBase entrypoints for caseeqsplit and friends

Now use case_eq everywhere.

Work on github issue #345

Automatically prove "case-eqsplit" theorems and store in TypeBase

For :num, this theorem looks like

(num_CASE n zc sc = v) <=>
(n = 0) ∧ (zc = v) ∨ ∃x. (n = SUC x) ∧ (sc x = v)

Such theorems can be powerful rewrites when (large) case-expressions
are asserted to be equal to some value or other.

These theorems have to be installed somewhat by hand for early types,
but from list onwards, the Datatype package handles this. This work
leverages earlier work done implementing prove_case_eq_thm (8f16922426).

Take the opportunity to rework TypeBasePure's code to use
FunctionalRecordUpdate.

This is progress with github issue #345.

Move pair, one, sum and option into one combined coretypes directory