Removed junk files and empty folders.

Removed junk files and empty folders that do not make sense to store
under source control.
Removed duplicated project.

Removed the Sitecore.ItemBuckets.BigData project that is duplicated by
Sitecore.BigData project.
Updated references in the projects.

Updated references section in each projects to avoid unnecessary
assemblies.
Removed unnecessary project from solution.

Removed unnecessary Sitecore.ItemBuckets.BigData project from solution.