[W.I.P.] Curve Tools plugin

[micheus]

I hope in a month or two.

I still finishing the drawing code review and implementing the selection stuff.
After that I may make it available for usability evaluation, but it will not have use without the window I have to create to manage the curves as well as all the options to allow us to create objects using them.
So, it's a long way to get something really useful.

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Just a background history...
The idea to work in a curve plugin started in 2012 with a basic plugin ready in 2013.Since there until 2014 I exchange a couple of messages about this subject with Fonte Boa, oort, Arg Arg and ggaliens. At some point that year I lost the source code (it was in a memory stick that I lose). After that I got involved with the bug fix and some conversions from the old to the new UI interface for Wings3D.
Just because this year things are a bit quiet I had some extra time to use for myself in Wings3D and I decided to start the curve plugin from sketch and better them the first one.