fixes for #411, #412, #413
fixes for #411, #412, #413

- added $aeq op for abstract/loose equality
- cloned collections with unique constraints should now update
constraint correctly on update()
- updates violating unique constraint now emit ‘error’ event

note: should still be reiterated that using unique constraints without
collection cloning will enforce during insertion only. If you intend to
update objects and maintain unique constraint, use collection clone
option.

thrownblown/LokiJS,Thrilleratplay/LokiJS,Thrilleratplay/LokiJS,techfort/LokiJS,VladimirTechMan/LokiJS,runnr/LokiJS,runnr/LokiJS,ThomasConner/LokiJS,ThomasConner/LokiJS,techfort/LokiJS,thrownblown/LokiJS,VladimirTechMan/LokiJS