WIP - upgrade QC + Rails 4 + db lock page + NULLS LAST when sorting

This is a WIP and requires a bit of testing before merging.

Those are breaking changes.

Includes:
- [ ] upgrade to QueueClassic 3
- [ ] upgrade to Rails 4+
- [ ] adds a page to see db locks for the process running a job
- [ ] make the null show last when sorting 
- [ ] ...?
It is created with QC3 -> https://github.com/ryandotsmith/queue_classic/blob/66e6ac853993f287bedf1453c6fec3da3c4b886f/sql/create_table.sql#L10