Implement machinery to check that tactic results change acceptably

Used to implement checks that h.o. redexes don't remain, or have
decreased in count.

This is progress towards implementation of github issue #680.

Remove TABs in some source code, replacing them with spaces

Use Emacs's conception of how many spaces the TAB was
representing (and the M-x untabify command).

This may not line up with the author's original conception, but then,
using TABs makes it impossible to tell just what the original
conception was in the first place anyway.

Should probably script this over all of repository (excluding
makefiles of course), and use standard expand or col utilities rather
than emacs.

Remove eqtype declaration for term type

rename Ho_Net.empty_net to Ho_Net.empty

All similar structures (e.g. Net and Raw) use "empty" not "empty_net";
it seems right to follow a single naming convention.

Change src/bool to src/1 as a prelude to experimentation!