Add newtype row IDs to prelude. (#161)

Closes #147

Author: molpopgen

src/prelude.rs

@@ -9,3 +9,7 @@ pub use crate::TskitTypeAccess;
 pub use crate::TSK_NODE_IS_SAMPLE;
 pub use streaming_iterator::DoubleEndedStreamingIterator;
 pub use streaming_iterator::StreamingIterator;
+pub use {
+    crate::EdgeId, crate::IndividualId, crate::MigrationId, crate::MutationId, crate::NodeId,
+    crate::PopulationId, crate::SiteId,
+};