Implemented categories for paper
Merge branch 'master' of https://github.com/open-review/open-review into feature-paper-categories
Fixed tests
Added category functionality to ArXiv scraper
Improved tests for reviewform
Fixed database structure, fixed unpredictable test failures
Added category optgroups in form, improved category scraping
Fixed minor issues concerning debug settings
Added related_name=children to Category.parent
Categories moved to initial_data file, which are lazily loaded by PaperForm preventing DatabaseErrors.
Fixed some minor inconsistencies (e.g. strange newlines)
Merge branch 'master' into feature-paper-categories

Conflicts:
	openreview/apps/main/forms.py
	openreview/apps/main/tests/reviewform.py
Merge branch 'master' into feature-paper-categories