Adding support for PHONE_VERSION endpoint.

This PR adds support of a valid PHONE_VERSION response.

This fixes pebble's behavior sending a PHONE_VERSION request every few seconds.

Problem is, that this also causes the pebble to show an "Old phone sdk warning". (once upon connection)
I think the problem here is that the "prefix" is for the 1.x SDK, but it seams that no one knows the 2.x SDK message. (checked most pebble implementations out there)