Updated Util.isAbsolute(path) to return true for Azure absolute paths

- Azure absolute paths look like \\ip_address\volume\guid\guid\site\wwwroot\...file.js.
  Changed Util.isAbsolute to return true for paths that start with two backslashes.
Merge pull request #1740 from superic/master

Updated Util.isAbsolute(path) to return true for Azure absolute paths