Remove BP-Default from trunk. Release builds will still include BP-Default.

See #5212, and for background, https://bpdevel.wordpress.com/2014/04/16/grunt-coming-to-buddypress/
Find BP-Default on Github: https://github.com/buddypress/BP-Default

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8500 cdf35c40-ae34-48e0-9cc9-0c9da1808c22