Mark the `remote` option of the Modal plugin as deprecated.

Follow-up to https://github.com/twbs/bootstrap/issues/13087#issuecomment-46563760
Closes #13087 as WONTFIX.
Closes #13597 as WONTFIX.
modal docs formatting tweak

[skip sauce]
`remote` modal docs: mention jQuery.load and other JS options as alternatives

[skip sauce]
Merge pull request #14034 from twbs/deprecate-modal-remote

Deprecate the `remote` option of modals?