Pyyeti

Minor update to the nas2cam tools to accommodate later releases of NX Nastran. Some wording and code cleaning as well.

Relatively minor updates since last release:

- fixed bug in op4 reader for binary 64-bit integer files
- updated dsp.fixtime algorithm for finding the mode sample rate (performance issue)
- misc bug fixes and doc updates

There were three primary updates since the last release:

- Add the ERA tutorial (thanks to Natalie Hintz!) and updated many links in the tutorials.
- Add PEP 517/518 compliance (thanks to Ramsey Yunis!)
- Update pyyeti.datacursor to handle units (like date-time) better
- It also can handle NaNs better

There were other miscellaneous updates, bug fixes, and documentation enhancements. Also confirmed that pyYeti is compatible with Python 3.10.

This update is primarily about testing updates:
- switched from nose to pytest
- cleaned up some tests
- reduced useless warning messages during tests

Updated the README file.

There were no significant pyYeti changes from a user's perspective.

This is a bug fix and deprecation fix release primarily:

- add "RVAX" datablock to output of nastran.bulk.wtextseout
- also added the `namelist` argument for more user control of op4 output
- began updating build/install/test codes to more recent standards
- added failure example for the nastran.n2p.find_xyz_triples routine