Prevent browser caching in sendJSONresponse
LemonLDAP::NG version: 2.0.8
sendJSONresponse is not explicit about whether or not its output is cacheable
This can cause bugs, for example, the "renew" captcha button doesn't work in IE because it thinks /renewcaptcha is cacheable
sendHtml already sends cache headers since #1651 (closed)
We could simply do the same, I don't think many of our JSON endpoints are cacheable.