Fix and enhance System.Uri

Added further default ports to switch statement.

Updated member variables to match correct naming scheme for nanoFramework.

Added functions to match Full .net Uri for IsDefaultPort, IsFile, and Segments.

Modified AbsolutePath to prevent returning null.

Added member variables and properties for Fragment, Query, PathAndQuery, and UserInfo.

Switched null check in Ctor to handle empty strings as well.

Changed TryParseUriString to ParseUriString since Try implies that it won't throw an exception, which is not the case.

Added ExtractFragment and ExtractQuery functions to parse and remove the Fragment and Query respectively.

Modified uri string to only change character case when necessary, as some Uri's are case sensitive.

Added ParseUserInfo to retrieve user info from the input string without modifying it.

Modified scheme switch in ParseSchemeSpecificPart to avoid user info being treated as part of authority in http scheme and similar cases.

Author: mizady