Add caching support for default xprofile field visibility settings

These settings rarely change, and so are good candidates for persistent caching

See #1332

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7781 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Ack, typo. Fatal props boonebgorges

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7782 cdf35c40-ae34-48e0-9cc9-0c9da1808c22