Implement trackChanges and getChanges on observable arrays
Support sparse diffs in general
Make array change tracking return sparse diffs

… because it will be far cheaper for known operations
Beginning implementation of "skip diff algorithm for known operations"

Currently only knows about "push"
Support the remaining known operations
Enable change tracking tests in Node.js, and fix minified build
Switch to a "subscribe"-based API for receiving array changelists
Implement array change tracking as an extender that can be used with any observable.
Clarify that ordering of array changes is only undefined for replaced items (the added and deleted entries for that item can be in either order); the changes are always ordered by index.
Optimize cacheDiffForKnownOperation for similar operations.
Allow extender to not return a value if the target observable isn't replaced.
Ensure that the trackArrayChanges extender only modifies the target observable once
Merge pull request #695 from knockout/695-array-change-tracking

Add support of filters/projections for observableArrays