Add bmo extension InlineHistory

Displays bug report information shown on show_activity.cgi inline
as part of show_bug.cgi. This makes it easier to see which action
has been taken when by who (e.g. changes to priority, assignee,
or status).

Bug: 47256
Change-Id: I6efc6bd485e32b65b99f652074c325d2d623bfb9
Merge "Add bmo extension InlineHistory"