Store disc data in an intermediate object

This allows us to free the underlying (C-)DiscId object earlier.

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Add some more documentation

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Move documentation around

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Document MemoryErrors

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>
Remove all the internal asserts

They are no longer needed as the user does not access them anymore.

Signed-off-by: Sebastian Ramacher <sebastian+dev@ramacher.at>