Complete the Sort plugin

[akagomez]

As far as I could tell the Sort plugin was largely incomplete.

After a lot of work it now...

• Two-way binds a can.List's sort order to the DOM
• Makes the fewest amount of DOM manipulations possible when rendered with {{#each}}
• Ensures that operations like push, unshift, and splice add items at the correct index via can.List._getInsertIndex() (for efficiency there's no need to append then move an item)
• Operations that result in an item being moved from one index to another result in a move event (this used to result in a remove and add event)
• DOM manipulations made on behalf of the {{#each}} helper move the underlying DOM nodes rather than removing and re-creating them (this is much faster).
• Resolves index changes to individual items with can.List._getInsertIndex as opposed to a complete can.List.sort operation
• Changes to items in the can.List that have a batchNum result in a complete can.List.sort operation rather than (potentially) lots of far less efficient can.List._getInsertIndex operations
• Breaks from can.List.sort operations when a partial sort is all that's needed to resolve the entire can.List's sort order

Future goals:

• Rough out documentation
• Choose a more efficient sorting strategy when there are no {{#each}} dependencies
• Benchmark this implementation of the Sort plugin against https://github.com/Matt-Esch/virtual-dom

Closes #1404, #1114, #1265, #828

[asavoy]

+1 This looks awesome

[imjoshdean]

👍

[matthewp]

This might need to be redirect to minor. @daffl is that right?

[daffl]

No. Master is up to date and ready for 2.2. Ideally things go against master now but it doesn't really matter since I need to merge minor in again anyway.

[marshallswain]

If you can sneak it into master, that would be awesome.