expose server name and port through WebContext
added support for using non absolute callback urls. if the server is accessible from multiple domains, it will dynamically build the callback url and redirect back to the correct host.
support dynamic callback urls for all clients, not just CasClient
use correct scheme for J2E web contexts
added test to ensure prependHostToUrl method uses the correct scheme
added enableContextualRedirects property to BaseClient so consumers must explicitly enable that behavior if needed
Merge pull request #18 from xargsgrep/master

dynamic callback urls