Prevent pre-populating date fields

On the tree detail page, the actions edit->save->edit would cause any
date fields on the page to be populated with the current date. This was
caused by the fact that calling "getDate" on the date picker will always
return a value, even if the text box to which the date picker is
connected is empty.

Fixes #1581
Merge pull request #1586 from jwalgran/topic/prevent-prepopulating-date-fields

Prevent pre-populating date fields
Unlocalize comment id in HTML attribute

Saving threaded comments was failing because id 1000 was being added to
the DOM as "1,000"

Closes #1594
Merge pull request #1597 from jwalgran/fix/threadded-comment-unlocalize-id

Unlocalize comment id in HTML attribute
Add comment moderation action endpoints

This includes the flag/unflag endpoints for use by the plot detail page
as well as the moderation endpoints for hiding, archiving, and flag
clearing.

I chose to create an EnhancedThreadedCommentFlag model because the
built-in CommentFlag does not support hiding, and I though having our
doubly-inherited comment model link back to another inherited model
would be too confusing, or perhaps impossible.
Change instance comment base endpoint

I made endpoints for flag and unflag and these look most natural as

POST /{instance}/comments/{comment_id}/flag/
POST /{instance}/comments/{comment_id}/unflag/
Merge pull request #1602 from jwalgran/topic/comment-moderation-backend

Comment moderation backend
Add grunt watch task.
Merge branch 'release'

Post-deploy merging of the release branch back into master.
Update user migrator to keep best username
Add CSV endpoint for duplicate user email mgmt
Merge pull request #1601 from steventlamb/topic/migrator_user_management

Topic/migrator user management
Merge pull request #1603 from kdeloach/topic/grunt-watch

Add grunt watch task.