Get rid of STuple and ITuple

we now use IcyClient since is more complete

TODO: IcyClient will probably renamed IcySource
Change on login and user privileges

LOGIN PROCESS is now changed:

* "source" can be used as username like any other
* password cannot contain pipe chars ("|")
* if password contain a pipe, it is splitted in two and treated
  as [username]|[password]
* login for GET requests can only be via WWW-Authenticate

* privileged sources ("admin", "root" or anything else) now are
  inverted: 0 is admin, >= 1 are every other source; also, sources are
  ordered by user privilege; if a.privileges < b.privileges, then a
  comes first