In BP_Groups_Group::get(), pass method params to SQL filters

Easy access to the original method parameters will make it easier for
plugin authors to customize the query intelligently. See, for example,
the case of sticky groups, discussed in #2242.

Props imath

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7376 cdf35c40-ae34-48e0-9cc9-0c9da1808c22