slightly refactor exports and access modifiers (mostly containers)?

[KonradHoeffner]

I'm not an expert in the Rust module system so I can't really articulate the exact problem but especially now, with most types having their own error type, I wonder if the use / pub use / mod / pub mod structure can be made more elegant.

For example here in hdt.rs:

use crate::containers::rdf::Triple;
use crate::containers::{ControlInfo, control_info};
use crate::four_sect_dict::{DictError, DictReadError, IdKind};
use crate::triples::{ObjectIter, PredicateIter, PredicateObjectIter, SubjectIter, TripleId, TriplesBitmap};
use crate::vocab::*;
use crate::{FourSectDict, containers};
use crate::{header, header::Header};

containers/mod.rs:

/// In-memory RDF representation.  
pub mod rdf;

/// Variable length numbers.
pub mod vbyte;

// byte containers
mod adj_list;
pub mod bitmap;           
pub mod sequence;

// control info section reader
pub mod control_info;

pub use adj_list::AdjList;
pub use bitmap::Bitmap;  
pub use control_info::{ControlInfo, ControlType};
pub use sequence::Sequence;

Can we improve this or is it fine as it is? Should we re-export the containers in lib.rs so that one can for example just use hdt::sequence::Error instead of hdt::containers::sequence::Error?