Address validation switch

Fixes #3344.  Only validate addresses if `dosomething_user_validate_address` variable is set to TRUE.

`dosomething_user_update_7006` will set this to TRUE for US but not set it for all other sites.

Also adds a custom access callback to the UPS API settings page, which checks to see if the variable is TRUE.  Also removes the "administer UPS configuration" permission and just checks for "administer modules' instead, in the interest of simplifying.
It's better to add the return FALSE at the end to be more explicit.