Don't use extract() in BP_Blogs_Recent_Posts_Widget

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7064 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Make the title of the Recent Networkwide Posts widget editable by the admin

See #4982

Props lenasterg

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7065 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Adds link_title support to Recent Networkwide Posts widget

This allows admins to decide whether they'd like the title of this widget to
link to the Sites directory.

Fixes #4982

Props lenasterg

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7066 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Miscellaneous cleanup in BP_Blogs_Recent_Posts_Widget

- Adds 'description' param to the constructor, to provide better context for
  admins using the Dashboard > Widgets panel
- Adds 'classname' param to the constructor, to ensure that widget styling is
  properly applied on secondary sites
- Use WP_Widget::get_field_id() for label "for" attribute, as per spec
- Whitespace

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7067 cdf35c40-ae34-48e0-9cc9-0c9da1808c22