The tskit prelude

The contents of the crate prelude are:

//! Export commonly-use types and traits

pub use crate::tsk_flags_t;
pub use crate::TSK_NODE_IS_SAMPLE;
pub use streaming_iterator::DoubleEndedStreamingIterator;
pub use streaming_iterator::StreamingIterator;
pub use {
    crate::EdgeId, crate::IndividualId, crate::Location, crate::MigrationId, crate::MutationId,
    crate::NodeId, crate::PopulationId, crate::Position, crate::RawFlags, crate::SiteId,
    crate::SizeType, crate::Time,
};