Only show the 'to disable' notice in emails if Settings is enabled

Unless Settings is enabled, these links will 404. This is not exactly a
regression, but it has become much more visible in BP 1.7, since the Settings
component is no longer enabled by default.

Fixes #4923

Props r-a-y

git-svn-id: https://buddypress.svn.wordpress.org/trunk@6917 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Use event delegation for AJAX buttons in Groups and Members directories

In r6635, BP's use of the deprecated jQuery.live() was switched to jQuery.on().
However, the change was not made in a way that preserved the behavior of live()
with respect to items added to the DOM dynamically, as per an AJAX callback.
We replicate that behavior by using jQuery.on() delegation on a persistent
parent element. That way, group directory buttons (Join/Leave) and member
directory buttons (Add Friend/Remove Friend) continue to work even when the
view is refreshed via AJAX, as in pagination or reordering.

Fixes #4931

git-svn-id: https://buddypress.svn.wordpress.org/trunk@6918 cdf35c40-ae34-48e0-9cc9-0c9da1808c22