IntanRawIO: Update support of rhs files (NeuralEnsemble#1457)

* initial fixes

* oops

* add in dtypes and channel numbers for rhs

* add test files in tests more fixes

* Fix naming of test files

* Update neo/test/rawiotest/test_intanrawio.py

* Fix pointers to test files

* oops

* dtype fixes

* split rhs and rhd + fix timestamps

* put streams in correct order

* fix test file naming.

* typo fix

* make sure stream_ids are sorted

* fix one-file-per-signal