Revert "Revert "Move getLocalStream() and getRemoteStream() to prototype""
Revert "Revert "Move getLocalStream() and getRemoteStream() to prototype""

This reverts commit 3a26c8ddf1a1fb8cd39b9dbb06220c9f27dd3af1.

Change-Id: I106c434811f1d0454824abf7b130a8136efbfb46

Kurento/kurento-utils-js,Kurento/kurento-utils-js,Kurento/kurento-utils-js