Refactor to support RemoteUrlSourceService

Using the more generic UrlSource, we can now configure those sources to
be retrieved from a remote file.  To use, upload a file containing the
Url, GroupName, and DataServiceType as comma delimited values for each
UrlSource, seperated by newline character.  For an example see:
http://pjdecarlo.com/playground/remoteUrlSourceExample.html

Starting to consider possibility of local/remote AppSettings file in
light of recent changes.  Why not let the user configure the entire app
remotely at this point =)