SEQ IDs are not inherited from parent activity

[bashbash]

winner https://jira.jpl.nasa.gov/browse/AERIEQS-273 Moderate When giving an activity which is a parent a Sequence ID, that Sequence ID is not flowed down to the children. Each child has to be manually given a Sequence ID.

I would expect that updating the parent activity's SEQ ID would at a minimum update the SEQ ID for all children which have not been manually set a SEQ ID by the user. There may still be an open question on whether we want parent IDs to override children IDs in all cases.

This is related to AERIEQS-272 Can't add SEQ ID to activity before simulation and AERIEQS-274 Sequence IDs not persistent in a plan.

[biqua]

New issue links are #798 and #796 (to replace the AERIEQS references above.)