Configure LDAP authentication
Make LDAP authentication / signin work

- Make LDAP authentication work without some essential features
  (saving e-mail address, grabbing data from LDAP server, etc.)
Fix LDAP authentication and make it work

- LDAP authentication works

- Remove offending line with `attr_accessor: :cnet` in user.rb
Replace user.email with user.display_name in views

- Make views more human-readable by replacing users' e-mail addresses
  with their names where appropriate
Fix devise :validatable bug in user.rb

- Users are now validatable
Add appropriate flash keys to SessionsController

- Override Devise's SessionsController with appropriate flash keys to
  make sessions pages more human-readable
Remove signup; update sample data with user info

- Remove signup links and routes

- Update sample_data.rake with cnet, first_name, and last_name info for
  users
Make users not devise :registerable
Merge branch 'ldap_authentication' into new_ldap

Conflicts:
	Gemfile
	Gemfile.lock
	app/views/devise/sessions/new.html.erb
	app/views/evaluations/_evaluation_short.html.erb
	app/views/evaluations/new.html.erb
	app/views/layouts/_header.html.erb
	app/views/pages/_submission_short.html.erb
	app/views/submissions/_submission_short.html.erb
	app/views/users/_affiliation_form.html.erb
	app/views/users/index.html.erb
	db/schema.rb
DRY up pages controller
DRY up new and edit quarter forms
DRY up application controller and helper
Refactor a few things
Fix some small bugs