Implement Pagination for Content libraries

[Kelketek]

• Background: This PR provides pagination for content Libraries in the container view, when displaying the blocks contained in the library.
• Jira tickets: Implements SOL-4
• Discussions: Architecture discussed extensively on the wiki and in meetings, then the revised proposal was presented to the Arch Council on Oct. 21 and given thumbs up.
• Dependencies: https://github.com/edx/edx-platform/pull/6046 (merged, in feature branch https://github.com/edx/edx-platform/commits/content-libraries)
• Sandbox URL: TBD
• Internal code reviews PRs: Content libraries paging #9 Implement Pagination for Content libraries #18
• Partner information: 3rd party-hosted open edX instance, for an edX solutions client.

[e-kolpakov]

Most likely it would make sense to log actual error with log.exception(message). Also, upstream reviewers (sarina mostly) often point out that logging is more efficient using log("something with %old_style format parameters", parameter1, parameter2, ...)