Provide the ability to white-list custom URL schemes in commit message

Problem Definition

Stash appears to be white-listing the URL schemes for URLs in commit messages. Some custom URL schemes (e.g rdar://) The rdar scheme is not included in the white-list. This means that the URLs are converted into a link, but the href attribute in the <a> tag is not present.

Suggested Solution

Stash should support a configurable white-list for URL schemes, and Users should add rdar to that list.