(bug 44385) clean up jquery.collapsibleTabs vs ext.vector.collapsibleTabs

Moving some stuff (essentially default settings and monkey-patches)
from the latter to the earlier. Also minor code cleanup and comments.

Change-Id: I62aeb2b6ba5f48fc19662812914e3545940dcd4d
Merge "(bug 44385) clean up jquery.collapsibleTabs vs ext.vector.collapsibleTabs"