Revamp the project.

* plainly and explicitely state that Eon3D is derived from plush
* bundle my fork of plush-1.2.x (boldly marked 1.2.1)
* restart eon3d core as amalgamation + rename of plush 1.2.x
stress the fact we're using a derivative version

both as basis for Eon3D renderer core and as bundled
reference.