Moved the code for constructing edition dict from ia metadata to core.ia.

That is generic code that can be reused in solr updater for some
optimizations.
Allow base_url to be either http:// or https:// in api client.
documentation and some cleanups to add_book code.
Allow importing IA scans by passing the identifer as input.

This makes it easier to import books into Open Library.
Optimized solr updates for bulk updates.