from Tom Edwards (artfunkel), with minor edits.
This patch makes the following improvements to environment map scripting:
* Adds a "is_valid" RNA property to envmaps. True if the map is ready for use, False if it needs rendering.
* Adds a "clear" RNA function to envmaps. Deletes any envmap image data.
* Adds a "save" RNA function to envmaps. Writes the envmap to disc with a configurable layout. (Defaults to the current hard-coded layout.)
* Updates bpy.ops.texture.envmap_save with configurable layout support as above.
These changes, particularly configurable layouts, make exporting envmaps to other software much easier.
0e01fa4863