XUriParser: changed char.IsLetter() to char.IsLetterOrDigit()
Merge branch 'UriParseOptimize' into DR-117
XUri:
* removed duplicate functions that now exist in XUriParser
* resharperized code
XUriParser:
* removed 'TryParse(string)' since this method now lives in XUri
* made all methods public to allow access from XUri

Unit tests:
* removed test for encoding in hostname since it's invalid
* fixed remaining usages of 'XUriParser.TryParse(string)'