Pull out external id so it isn't empty by default
Don't allow user to submit fake owner_id in upload
Owner id checking changes

Cache the owner id lookup to help prevent any slowdowns.

Include case sharing groups in valid owner id checking.

Do not process failed rows, alert user of those that failed.
Implement hints for sort direction

This was done then reverted and is now done properly using knockout
Merge pull request #705 from dimagi/case-importer

Case importer
Merge pull request #717 from dimagi/tiered-sort

Implement hints for sort direction
switch to min version of nvd3
check keys is None exlicitly
Merge branch 'repkey' into staging2
Merge branch 'nvd3min' into staging2
bump sqlagg version
bump unicef ref
Merge branch 'sqlagg' into staging2