Facette scan

[arowana755]

Add a function filtering some wrong mesh generations. It doesn't filter everything, but it can catch some poorly created mesh.

[edgar-bonet]

Thanks for the pull request! I still have to take a deep look at this code, but I quickly noticed a few issues, so I am requesting some changes that you can perform while I dig more deeply into the code.

First of all, there are quite a few changes here that have nothing to do with the purpose of the pull request: const correctness, moving a function from a header to a cpp file... These should ideally me moved to another pull request. At the very least, they should be in separate commits.

Other things that deserve fixing:

• avoid introducing compiler warnings; for instance “comparison of integer expressions of different signedness”

• avoid introducing trailing whitespace.

• in English, “facette” is spelled “facet”

• in English, there is no space before a colon (write “Error: …”)

• messages output to the terminal should end in '\n'

• also, please rebase on top of master