Fix validations on user settings page

Closes #3271
- Change validations on both server and client to allow the
  Website field to be empty or a valid URL.
- Add new schema validation helper isEmptyOrURL.
- Remove duplicate call to UserValidator in the save action
  of the SettingsUser controller.
- User.last_login and User.created_at are already Moment objects
  so Moment#fromNow can be called on them directly.
Merge pull request #3272 from jaswilli/issue-3271

Fix validations on user settings page
Server side cleanup

- remove sessions
- remove all references to csrf
- create a shared base model for the 2 types of token
Refactor settings routing and mobile interactions

Closes #3254, closes #3138, closes #3245
 ### Settings Routing and View refactoring
- Refactored `SettingsView` to handle transitions between mobile and desktop layouts
- `SettingsRoute` will only transition to `settings.general` if the screen is large enough to show both the menu and the content
- Added `SettingsIndexView` to handle showing the settings menu on mobile screens
- Added `SettingsContentBaseView` to be inherited by any settings view that is not index.
- Updated Settings templates appropriately to work with new views
- Removed extraneous `active` class from `settings-content`
- Changed settings menu to use `gh-activating-list-item`
- Retooled settings tests

 ### Mobile Utils
- Renamed file to `mobile.js`, since it's inside of `utils/`
- Added `mobileQuery` MediaQueryList to help detect layout changes
- Removed unused `hasTouchScreen`, `device.js` should be used instead.
- Removed unused `smallScreen` function
- Moved FastClickInit to codemirror-mobile