[SPARK-4797] Replace breezeSquaredDistance

This PR replaces slow breezeSquaredDistance. A simple calculation involving 40000 squared distances between the vectors of 20000 dims shows:

* breezeSquaredDistance:  ~12 secs
* This PR: ~10.5 secs


Apologies, I should have actually said there's no need to test anything here since ```v1Indices(kv1) == v2Indices(kv2)``` will always be true as well!