Allow 'noprotocol' option in captcha-addurl-whitelist

ConfirmEdit triggers a captcha when users without the appropriate
userright add new external links. But sometimes there are links that
these users should be able to add without a captcha, e.g. other wikis in
the same farm, so MediaWiki:Captcha-addurl-whitelist allows wiki admins
to whitelist links matching regular expressions.

However, these whitelist entries are automatically prefixed with
"^https?:\/\/+[a-z0-9_\-.]*". While this is usually what is wanted, it
prevents wiki admins from whitelisting other types of links such as tel:
or urn:. Following the example of TitleBlacklist, this change adds
options delimited with <> to the whitelist lines, and adds an option
'noprotocol' that causes that line to be prefixed with only "^" instead.

Bug: 56485
Change-Id: Ia0d484f7a4670df2c7121d1284e4fcf969e818c3
Merge "Allow 'noprotocol' option in captcha-addurl-whitelist"