* added support to the utility class Triangle for the region growing block
of the segmentation (implemented properties and methods to describe "seed"
triangles)
* added utility class Edge that implements functionality for a triangle
edge as defiend by two distinct vertices
* refactored util classes DrawObject and Triangle to align them to new
class Edge inside the same package
* added multiple methods to Triangle as helpers for the EdgeAnalyser and
ModelProcessing classes from knowrobcad_mesh_reasoning
* shutdown pool when threads finish to avoid memory leaks