Add UNC and file:// support

I have need for links to intranet resources via UNCs. I have added support for this. Users enter a UNC and if the "Title as UNC/URL link" formatter is chosen, the UNC will be displayed as a file:// link. The original UNC is stored in the DB. Note that these types of links work natively in IE, but not FF. There are two work-arounds for Firefox which I note in the formatter's comments. Basically, you can either set certain preferences or you can install an add-on called ietab to get those links working. I prefer the preference settings method.

I haven't extensively tested the alternative which is to have your users convert backslashes to forward slashes and place a "file://///" at the beginning of their path when they enter it in. FF requires (?) the five forward slashes IIRC.