Naming ports

Hi, I've just removed the device-mapper port from contrib because opt has a "libdevmapper" port of the same project. Thanks to Alan Mizrahi and Simon Gloßner for noticing. This shows how redundant work can happen because of badly chosen port names. So, perhaps a naming scheme could be set up to aviod such in the future. Personally I use the wording I'd use when mentioning the project, e.g. "do you have a recent version of mesa?" - not mesa3d.