Changing text/char fields in EMBBEventLog model to blank=True as appropriate, also adding N/A option for observation status field.

Conflicts:
	gracedb/models.py
	gracedb/urls.py
	gracedb/views.py
	manage.py
	templates/gracedb/event_detail.html

Added N, created to EMBBEventLog. The N is for addressibility, along the lines of the EventLog object.

Removed SimpleSearchFormWithSubclasses. The only thing that needed this was the gstlalcbc report page, and there is a simple workaround instead: just get a list of Event objects, and upcast them to CoincInspiralEvents. One wrinkle is that the matplotlib call 'fill_between' (which had given us that nice grey region on either side of the expected IFAR line) seems to hang now. I emailed Chad and commented this out.

Fixed bug due to Django 1.6 update. The get_or_create call in refresh_users_from_ldap.py needed some default arguments. Otherwise, it tries to create a user with an empty username, and that will collide with another user with an empty filename and cause an unhandled exception.

Removed settings/update.py and modified branson.py to reflect updates. No changes required for settings/default.py