[BACK_INCOMPAT] Possibility to remove multiple `fabric.Objects` from collection (canvas, group) 

[BACK_INCOMPAT] Possibility to remove multiple `fabric.Objects` from collection (canvas, group) 
`this` (canvas, group or object) is returned instead of deleted object
Update unit tests - use strictEqual for some cases
Add multiple objects raised `object:added` for last added object first - now 1st added object raises 1st `object:added` event, 2nd object raises 2nd `object:added`…

Closes issue #963