Update the placeholder text for the sitewide search box.
Remove mention of the Sets Controller, which was actually being used for nothing.
Modify search partial to allow for passing of local 'scope' variable.  If set this variable will be used to construct a scoping filter to apply to the query.
Adds scoped queries that work over collections + communities.  Just need to make them work over the 'fake' smart collections that exist attached to communities now.
Updates the scoped search box to have appropriate placeholder text and no extra Search button, which was ugly.
Merge branch 'collection_search' into develop

Merging in changes w.r.t searching scoped collections that are technically only halfway done.  This adds the ability to perform a scoped search over Communities or Collections but **not** over the smart collections assembled on the fly under Communities.  This implementation is somewhat naive in that it generates a filter query with rather a lot of connecting OR boolean statements.  Discussion on tickets related to Solr 4x [here](https://issues.apache.org/jira/browse/SOLR-4586) seemed to indicate me that the number of unique boolean statements can grow _very_ large without necessarily posing a problem.  References #434.