Clean collection UDF values before showing them on the plot detail page

There was machinery in place to do this cleaning, but it requires retrieving
collection UDFs through the 'udf' property on UDFModel
Add support to udf_defs cache for getting all UDF defs for an instance
Clean audit values for UDFCollectionValue and scalar UDF audits

Also formats dates as part of Audit.current_display_value and
Audit.previous_display_value
Merge pull request #1609 from maurizi/fix-udf-date-formatting

Fix UDF date formatting
Factor out and fix helpers
Refactor synchro user exports to be more semantic

Views are now in the views file and exported accordingly. Helper
functions to also be used for asynchronous exports are factored out
into the helper module
Make export js dynamically load export buttons

Instead of providing a single initializer that takes information about
the dom, read the dom and enable exporting for controls that provide the
necessary start url.

The export js now supports multiple job intializers and checkers with a
centralized job manager to make sure jobIds don't get crossed up.
Add views and tasks for async user exports