Revert "Remove obsolete IP_HIDDEN column from peer list." Closes #970.

This reverts commit c8d51e91f415dcef4ce77569cb8d9ac794c41c5f.
Partial revert of e7c27c9b8b. Single file preview works again.
Prepare bandwidth scheduler code
Merge pull request #983 from Gelmir/sched_fixup

Remember Alt bandwidth on shutdown.