diff for PR
form filters properly for edit/create dataset
single bundle/multibundle selection
adds migration
adds select2
makes data_file optional, form validation stuff, 'the whole 9 yards' :)
remove cruft -- not needed, just had to set null=True, blank=True for that file field
downloading bundles done, form behaves nicely based on multi/single
removed editing button for datasets, referencing super bundle in competition works
merged master, fixes up template
Merge pull request #590 from codalab/feature/sub-bundles

Sub bundles