Implement Pagination for Content libraries (SOL-4)

* **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**: http://sandbox.opencraft.com:18010/library/library-v1:TST-X-01+now
* **Internal code reviews PRs**: https://github.com/open-craft/edx-platform/pull/9 https://github.com/open-craft/edx-platform/pull/18
* **Partner information**: 3rd party-hosted open edX instance, for an edX solutions client.

@singingwolfboy @Kelketek `library_container` mostly interface with [views/container.js](https://github.com/edx/edx-platform/pull/6163/files#diff-491ea957c87c066ecd89e580ab34fb46L126). `refresh` is called in [pages/container.js](https://github.com/open-craft/edx-platform/blob/content_libraries/4-pagination/cms/static/js/views/pages/container.js#L145)

So this empty function here is to provide `refresh` method that does nothing. I must have a good reason to not use it to refresh an XBlock, but I can't recall right now. I'll update you if I recall more about that.