added angle-parameter to extract surfaces more precisely
formatting
find x
changes based on PR comments
removed binary file and fixed intentation
exchanged pi-constant for radian-constant
added doxygen filename tags
Reduce indentation by reordering if clause.
Use std::size_t instead of size_t.
getSurfaceAreaForNodes() returns its result.

Also correct a description.
manually added changes by @endJunction that couldn't be added due to merge conflicts
replaced boost::radian with boost::pi again because the former didn't give the desired result
Merge pull request #488 from rinkk/SurfaceExtractionRefinement

Refined mesh surface extraction