Updates and applies JSHint settings

- Adds all available enforcing options in JSHint rake task.
- Removes unsupported options in JSHint rake task.
- Cleans up JS according to stricter JSHint settings (with 2
exceptions: the regex in the feedback form manager and the many
statements warning in the function in the popup-manager).
- Refactors character limiter code to use event handler function.
- Removes unused code from details map manager code that was leftover
from when the nearby markers were present.
- Removes enquirejs and associated code from the popup-manager.
This was used for turning off the popups at small screen sizes,
however it had been disabled because it caused issues in IE.
If these can be converted to symbols, then do this: `requirejs: false`, otherwise use hash rocket but single quotes, like this: `'requirejs' => false`