[642] Fix error with inventory.jobs getting converted to string when saving the Group itself. Fix saving of publish_date when from CSV. Fix display of publish_date in dataset/read.

Conflicts:
	ckanext/dgu/controllers/inventory.py
[642] Publication Date field is now validated on import and only displayed if a proper date. Those that have uploaded non-dates will not see them at dataset/read.
[642] Convert dates to the preferred format in the DB, as used for other date fields.
[642] Search box is "Results" on /data and /data/search and never "total datasets" as that would confuse with number of Datasets on the home page.