start the heap construction: load from a heap is done... store, CAS, and singleton (mapsto) to be done

On branch master
	modified:   algebra/fin_maps.v
Untracked files:
	heap_lang/heap.v
no changes added to commit (use "git add" and/or "git commit -a")

Also, do some cleanup, like declaring Params instances.

(missed practically everything in the previous commit)

Also, make our redefinition of done more robust under different
orders of Importing modules.

Since Coq 8.4 did not backtrack on eauto premises, we used to ensure
that hints like

  Hint Extern 0 (?x ≡{_}≡ ?y) => reflexivity.

were not used for goals involving evars by writing ?x ≡{_}≡ ?y instead
of _ ≡{_}≡ _.

This seems to be a legacy issue that no longer applies to Coq 8.5, so
I have removed these restrictions making these hints thus more powerful.