Geometry_Engine: add a method joining unordered lines into closed loops

[pawelbaran]

Description:

A feature requested by one of the users, to take a set of unordered, collinear lines and turn them into a set of closed loops that can be extracted, e.g. from the following set of lines:

... we would get following 6 outlines returned:

...this will also enable reconstruction of meshes from their edges.