If the id of a `.formulaequationinput input` element contains a special
character, then the selector for $preview was silently failing to match
the element, because no escaping was happening.

This fixes the issue by escaping the id before passing to the jQuery
selector function. CSS.escape is the ideal method, but this isn't
present in IE or Edge, so we use a fallback borrowed from the new
jQuery.escapeSelector method.

Improve accuracy of javascript-escape linter: Previously this would
match on FOOescape() and FOO.escape calls, but neither are the global
escape function we are worried about.

The regex probably isn't 100% accurate; there may be still false
positives (javascript allows a large range of characters in identifiers,
some of which may not be covered by [\w.$]). The main thing is to avoid
false negatives here though - this will definitely catch any use of
`escape()` or `window.escape()`.

Also remove javascript-interpolate lint - this was deemed unecessary.
StringUtils.interpolate is not in fact safe (it does no html escaping),
so the results of this lint are misleading.

…d-selector