Retire MPD

[Michael Horvath]

If I remember correctly there was confusion among the casual user that a ldr file could not only contain dat files, so parts, but also other ldr files called submodels. From an organisational point of view it should be handled like this:

dat - parts
ldr - single model
mpd - multiple models

w.

Don't forget XMPD! Meaning, an LDR file should be able to contain parts, submodels, and multimodels. For organizing large multi-user projects this is critical!

But as long as the format is recursive and can later be "unpacked" to however the designers originally intended the models to be it doesn't matter what the extension is.