New point finding algorithm for graphs.

Changed used data structure from approx-two-dimensional hash tables to
Quad Trees. Added tests for both Quad Trees and graph distance sequence.

Closes 68
Fixed graph distance sequence.
Added comments.
Fixed issue 68 again and renamend EmbeddedGraph.
New 3D graph class.

Closes 71
Graph distance sequence contains each element twice.
Deleted constant.
Merge pull request #104 from progma/issue68+71

Fixed issue 68 and 71