Allow to overwrite URL_REGEXP in urlInputType:urlValidator

[raulfraile]

Apparently, when using type="url" with ngPattern to validate the data, angular checks first if the URL is valid according to the URL_REGEXP regular expression, and then validates the pattern. So, the data will be valid if matches both regexps.

As URL_REGEXP only allows basic/standard protocols (http, https and ftp), it is not possible to use the url type for URLs such as git://..., ssh://... or just myprotocol://..., which can make sense to use in an application.

Having an option to disable the url validation when using ngPattern would fix the issue.

[caitp]

@IgorMinar WTDY of this? It shouldn't be too different from navigator.registerProtocolHandler(), I mean if the platform exposes that, there's probably no reason why we couldn't have a similar thing, for both ngSanitize as well as the form controls

[caitp]

Anyways, I'm not sure how frequently this gets run into, but I don't think it should take much code to support, so unless someone says otherwise, PRs welcome