Merge pull request #70 from tjhei/update_manual

update contributors and manual.pdf
Now always remove the radial component of velocity from the GPlates plugin.

Before the removal we check that this component is small, to ensure the rotation and projection is working properly. If it is small and we do not want to have it in the solution we might as well remove it completely.
Add an assertion.
Add find_postprocessor
Bugfix and add test
Using NULL instead of 0
Update changes.h
fix compilation and test output

this merges pull request #72:
https://github.com/geodynamics/aspect/pull/72
Add a test for the existing GPlates plugin.
Implement patch for GPlates 1.4

The patch checks for the version of the provided gpml file and also
includes an assertion against creating an unreasonable mesh.
Add test for the new GPlates 1.4 patch.
Update the manual for the GPlates 1.4 patch.
Updated changes.h.
Improved the version check for gplates.
Another bugfix for gplates version check.
Merge branch 'gplates-1.4-patch' of https://github.com/gassmoeller/aspect

Conflicts:
	doc/modules/changes.h

https://github.com/geodynamics/aspect/pull/73
Do not include unused header
update .gitignore
Made compositional IC plugins ready for being derived from SimulatorAccess.

Removed the geometry_model pointer that was stored as default in interface.cc
Remove an outdated TODO, leave a new one.