Also added a few notes to the documentation

- Updated ibug2did.txt with a description of the contour indices
- Added a file describing the left and right model contours (the face outline) on the reference model
- Caveat: The implementation is a bit poorly documented for now

* texture is now correctly a boost::optional

Notes:
* Removed the runtime-check in get_mean_at_point()
* I couldn't find out whether ::rowRange has a bounds check in debug builds. Therefore, added an assert.

Conflicts:
	README.md

Added comments to texture extraction

mainly on the texture interpolation methods

v0.6.0: OpenGL-like rendering, texture rendering, texture extraction view-angle computation

fit-model: Replaced affine camera estimation with nonlinear algorithm (allows direct recovery of the pose angles)

This should make the app easier to understand, i.e. remove anything that's not necessary.

Fixed last commit, added helper functions for glm/Mat and get_4x4_modelview_matrix(fitting::OrthographicRenderingParameters

Wrapped the extraction of a triangle in a lambda and calling all lambdas with std::async

At the moment, only TextureInterpolation::NearestNeighbour is adjusted to work