Move a few things around, make orthographic zoom work

Moved the enum to the camera for the projection type, improve the
scale function to be aware of perspective and orthographic scale.
Added some logic to the navigate tool to zoom properly for both
projection types.

Change-Id: I4c725b2ac4140579e7a169833f0d296720979390
Minor documentation update

Change-Id: Ieab1d1c5b918517950a26a0d95836b172ca822db
Merge branch 'ortho-zoom'

Change-Id: If1e45da4d983b04e63a86690531a7b389ebbc6d3