Update romanisim following RTB review

[stscijgbot-rstdms]

Issue RCAL-771 was created on JIRA by Eddie Schlafly:

Andrea, Charles-Philippe, and John took a look at the simulator as part of an informal science validation (excluding L1 questions).  They identified a number of minor changes that are needed in the simulator, including:

• support for truncation
• more metadata
• more consistent treatment of roll angle

This covers that work.

[stscijgbot-rstdms]

Comment by Eddie Schlafly on JIRA:

Done in spacetelescope/romanisim#99