Enable doxygen for MeshGeoToolsLib.
[MeshGeoToolsLib] Base class for search length algorithms.
[MeshGeoToolsLib] Heuristic search length.

Computes the search length using a heuristic.
[MeshGeoToolsLib] Impl. of fixed search length.
[MeshGeoToolsLib] Using search length in MeshNodeSearcher.
Using new MeshNodeSearcher interface in Tests.
[MGT] Handle case where standard deviation of edge lengths is very small.
[MGT] Add assertion in MeshNodesAlongPolyline algo

Epsilon must be a positive value.
[MGT] Typos, empty doxygen fields, include paths.
[MGT] Remove unnecessary check.
[MGT] Var. rename improves readability.
[MGT] Replace iterative search with explicit solution.
[MGT] Introduced search_length as parameter in base class.
[MGT] Replaced FixedSearchLength with SearchLength.

Moved functionality of FixedSearchLength to SearchLength.
Make SearchLength default in MeshNodeSearcher ctor.
Merge branch 'ufz/pr/480' into CLISkeleton.