Tidy pair{Script,Theory,Simps} to have less cruft

In particular, it's desirable to reduce the number of calls to
augment_srw_ss outside of Script files.

Change "thm-names" (used in various places) to be Thy-Name record

This saves on pulling things apart and looking for dots and the like.
It changes the simpLib API (most significantly for the SSFRAG function
which builds simpset fragments).

Give theorems names in simpsets

This is to allow them to be removed easily. System builds on -t1, but
there are still two things to be done

1. the names associated with export_rewrites calls aren't passed on to
the simpsets yet
2. there is not yet an API for removing them

Also, perhaps just as an interim measure, I removed the unused
entrypoint for removing rewrites by pattern matching against their
LHSes (simpLib.remove_theorems).

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