crate organization + stuttering

[emberian]

the way the crates are organized right now, there is a lot of stuttering in the names. there are also multiple public paths to the same items, due to public re-exports alongside public modules. imo, we should adopt the "facade pattern", where the external interface to a user-exposed crate is defined in a single place using public re-exports of pub(crate) items. this keeps the interface clean, and also makes rustdoc beautiful. more information about the pattern is indexed here. the goal is to avoid useless sections in rustdoc that look like this:

[emberian]

@prestwich do you have strong opinions on crate organization / naming?

[emberian]

my basic opinion is that if code is in a replica.rs to make the filesystem easier to navigate, the mod.rs containing it should make it so that users don't have to type path_to::replica::Replica but instead just path_to::Replica.