Add BLEND support using assimp plugin

[mwestphal]

Assimp library support BLEND format, lets add support for it

Related to: #38

Testing with #1123 , I tested the data from https://github.com/assimp/assimp

It looks like:

• Texture seems to be working : https://github.com/assimp/assimp/blob/master/test/models-nonbsd/BLEND/fleurOptonl.blend
• Some files produce empty output: https://github.com/assimp/assimp/blob/master/test/models-nonbsd/BLEND/Bob.blend
• Normals look weird (any file in assimp models folder)
• No crash to report so far

[Meakk]

My problem is any .blend file I generated from a recent Blender version is not working at all. I suspect the assimp support has been implemented a while ago and has not been maintained to support more recent versions.

[mwestphal]

My problem is any .blend file I generated from a recent Blender version is not working at all. I

Lets try with recent version of assimp, if still failing, lets open an issue.