Tweaks and improvements to fundamental/homography estimation

- A bit more reasonable name for the estimation option
  structure and estimation functions.

- Get rid of unclear function and parameter tolerance,
  it wasn't clear at all in which units they are.

  Now we've got expected_average_symmetric_distance as
  an early output check and as soon as average symmetric
  error goes below this threshold refining finishes.

  This distance is measured in the same units as input
  points are.

  It is arguable whether we need callback for this or not,
  but seems Ceres doesn't have some kind of absolute
  threshold for function value and function_tolerance
  behaves different from logic behind expected symmetric
  error.

- Added option to normalize correspondences before
  estimating the homography in order to increase estimation
  stability. See

    R. Hartley and A. Zisserman. Multiple View Geometry in Computer
    Vision. Cambridge University Press, second edition, 2003.

    https://www.cs.ubc.ca/grads/resources/thesis/May09/Dubrofsky_Elan.pdf
Fix T37172: Plane Tracker Deform - No perspective

Previous wrap implementation was based on inverse
bilinear mapping, which doesn't give perspective.

Now plane track wrap estimates perspective transform
matrix as a homography estimation between frame
coordinates and plane corners.

Uses Libmv's implementation for this, which means
plane track wouldn't work properly with Libmv
disabled. Not a deal for official builds at all,
just folks who keeps things disabled need to be
aware of this.
Expose track's offset to the RNA
Fix T37545: SV+H color cube display changes H slider position when modifying S or V.

The widget for the SV gradient was disabling display colorspace transform, but this was not happening for the H slider below, leading to varying H values used to calculate the slider position.
Bevel Fix for nonplanar faces / reflex angles

When beveling two adjacent edges, code used face normal instead
of the face-corner normal (these can be different for nonplanar
faces); the bevel may look uneven in such cases.
Switched to using corner normal, and needed to fix the case
where the edges meet at a reflex angle. Fixed a similar case
when beveling two edges with one non-beveled in between.
Also removed unnecessary argument from offset_meet.
Transform: Warp tool (rewritten)

* Can optionally warp a segment (sets min/max default so it acts as old warp did).
* Can rotate the warp axis (old warp tool was limited to horizontal).
Updating icons for NLA Track "solo" button (as used in standard widgets)
Skeleton of type defines for NlaTrack animchannel
Ported over logic for which animchannel settings are supported by NLA Tracks
Ported code for setting colour of NLA Track anim channel
Added button callback so that toggling solo mode on NLA Tracks now works correctly
Remove old drawing code for NLA Tracks
Anim Editors: Improve some tooltips to be more accurate for the type of editor/data they're shown for

This commit fixes some problems where some tooltips were not adapting
as intended when used for different channel types in different places.
Anim Editors: Ensure that "solo" flag doesn't get accidentally handled on channels which don't support it
NLA Channel Drawing Refactor: Remove rest of old drawing code for NLA Track channels

NLA Track drawing has now been ported over to use the UI widgets
like the rest of the anim channels do in the DopeSheet and Graph
Editors. The main benefit of this for users is that these buttons
will now show tooltips when you hover over them. Hopefully this
will help make the "solo" buttons more discoverable.

I've decided to postpone porting the "Action Line" channels to the
widget system for now, since there are quite a few more issues there
which need quite a bit more time to work through.
Fix T37550: Crash while snaping to curve made from Susane (bug in recent addition)
fix T37411: Transform mouse constraint could fail in some situations.

Was caused by int rounding when an axis was < 1.0.
Code Cleanup: remove unused members for editfont (3D text)
Fix T37543: Multiline 3D Text saved in edit mode breaks on load
Blender Internal:
* Remove Stars feature. This was a quite minimalistic feature and there are
better alternatives with more control (particles for example).

Removal discussed during BCon13 developer meeting and already years before, time to do it..

Reviewed By: brecht
Differential Revision: http://developer.blender.org/D17