Update info about epic owner role based on recent feedback.
cf. SE-240
In particular, this PR addresses a question from @pauloviadanna about "synchronizing with client boards". (That question was mostly specific to a particular client, but the general topic of keeping OpenCraft's JIRA in sync with external JIRA/Trello boards is relevant to the work that we do for other clients as well.) The changes from this PR are based on @__xitij__'s answer from this comment.
It also contains a couple drive-by fixes for the handbook item about epic updates.
Test instructions
None.
Reviewers
Edited by Tim Krones