DOC reclassify notebook as HOWTO

[prjemian]

As noted in BCDA-APS/bluesky_training#150, the examples/notebooks/tst_UB_in_descriptor_document notebook is actually a HOWTO.

[prjemian]

As stated in #257

This document is (partly) a HowTo. While leaving this document in place, make a HowTo document.

Focus less on how to create the diffractometer. Use a single geometry to demonstrate since that is the most typical situation. Refer to other documentation to describe how to create a new sample and how to create orientation information. The new HowTo should describe how to save and how to restore crystal orientation info. Also how to find runs with such info.