Tweak Selenium enumeration tests to run concurrently
Tweak rspec tests to use less memory
Have the user access test deal with lots of users
Have Solr trigger periodic auto commits
Be more selective when deleting records with children on update (mostly we don't need to do this)
Refactor pagination handling to support more pagination options
Add support for two new pagination options:

  * all_ids=true -- doesn't return records: just a JSON array of their IDs

  * id_set=1,2,3,4,5 -- returns the requests set of records (selected
    by ID)
Rework the periodic indexer to use the new 'id_set' pagination option.

This should make indexing faster for repositories with lots of
records.  The LIMIT/OFFSET approach used by the standard pagination
gets progressively slower as you seek towards the end of a dataset
(which indexing always does).  Instead, we pull back the complete list
of record IDs initially, then request subsets of IDs.
Be a little more selective with regard to which JSON exceptions we catch
Move temp file handling into the batch_imports controller so that retrying on failed transaction works properly.
Don't send a vocab changed notification unless the creation actually succeeds
Make sure the terms sha1 is always set
Make sure ensure_exists always fires (even under the raciest of conditions)
Transaction wrangling
Use a more efficient query for handling id_set queries
Merge pull request #430 from hudmol/loadtest-tweaks

Loadtest tweaks
Add hooks for overriding JSONModels and indexing
Added dynamic fields to the Solr schema
Add Solr search hook
Store information about which user created and last modified each record