Support non-SPNEGO authentication methods and implement session handling in REST java client library

The current java client only supports the SPENGO authentication method.

This does not support the case when an application proxy like Apache Knox performs AAA conversion from BASIC/DIGEST to kerberos authentication.

Add support for BASIC username/password auth the client.

Generally, the authentication code in the client looks quite backwards, it seems that most of the kerberos / auth cookie code duplicates HttpClient functionality. AFAICT setting HttpClient up (or letting user set it up) , and letting it handle authentication by itself would be a better and more generic solution.

Also add support for specifying a prefix for the URL path.