Clean up the module structure

[actioninja]

Essentially all code was unnecessarily put in a dmi module and then reexported at the crate level. This doesn't make a whole lot of sense.

All code was instead moved to live under the base crate module or whatever its relevant module was.

This is (almost) entirely an API compatible change. Due to the aforementioned reexport, all modules were used from the base crate level. Unless you specifically were referencing them by the full qualified module path, this shouldn't cause compilation issues.
Also what was in effect an integration test was in the main sourcepath instead of the tests folder, so that was extracted out.

One change was made for visibility. crc was changed to be crate local. I didn't particularly see a reason why this should be exposed. This can be reverted if needed.

[ZeWaka]

Been meaning to look at this, sry