Fixes #1866

Fixes #1866

Also added rudimentary position-based vertex colors to MarchingCubes object and example for testing.

There is no normalization or anything, it's up to application layer not to set colors beyond <0,1> range.

This addresses issue #1834

removing less necessary stuff from Path.js. May still have to decide whether to migrate to using .curves from .actions

As per suggestion in https://github.com/alteredq/three.js/commit/5d5f92d6411f3d39725ea704594d7a09ecb92cca

Fixed MarchingCubes bug introduced by previous commit. Added flat shaded material to marching cubes example.

Only these 4 are actually valid for regular textures:

http://www.khronos.org/opengles/sdk/docs/man/xhtml/glTexImage2D.xml

We had it wrong before, it just accidentally worked as default type GL_UNSIGNED_BYTE is common for both data types and pixel types.

Also added optional quick-and-dirty UVs for MarchingCubes object, just to be able to test this. For the moment these are just XZ world coordinates.

This should address half of #1834