fix(restate_axiom)

[kim-em]

This changes the behaviour of the command restate_axiom, to give better names:

• if a second argument is provided, use that as the new name, otherwise
• if the field end with a ', the new lemma has the same name without the ', otherwise
• the new lemma has the field name with _lemma appended

This PR also removes all the inappropriate [ematch] attributes on lemmas in the category_theory library. To use rewrite_search we'll have to add [search] attributes later.

Closes #282 and #283.