Lab - add polylines to selection of edges

[janetournois]

Summary of Changes

With this PR

• load a surface triangle mesh
• load a set of polylines (*.polylines.txt, or *.cgal, or *.txt)
• create a selection item containing the polylines as selected edges (in PMP -> Select edges)

Release Management

• Affected package(s): CGAL lab
• License and copyright ownership: unchanged

[afabri]

Warnings in I-c-348, but I think it is to early for the testsuite as there are todos in the code and lots of debug std::cout, which is normal as this is only a draft PR @sloriot

[afabri]

I guess the warning in I-c-351 comes from this PR.

@janetournois can you check if the plugin does what you want to achieve.
I can then throw out debug code and output.

[sloriot]

Successfully tested in CGAL-6.1-Ic-14