Change module structure

We can treat all functions related to SASL negotiation as a submodule
to Pontarius XMPP if there are no dependencies from the internal
Network.Xmpp modules to the SASL functionality. Because of this,
`auth' and `authSimple' were moved from Session.hs to Sasl.hs. As the
bind and the `{urn:ietf:params:xml:ns:xmpp-session}session'
functionality are related only to the SASL negotation functionality,
these functions has been moved to the SASL submodule as well.

As these changes only leaves `connect' in the Session module, it seems
fitting to move `connect' to Network.Xmpp.Stream (not
Network.Xmpp.Connection, as `connect' depends on `startStream').

The internal Network.Xmpp modules (Connection.hs) no longer depend on
the Concurrent submodule. This will decrease the coupling between
Network.Xmpp and the concurrent implementation, making it easier for
developers to replace the concurrent implementation if they wanted to.

As Network.Xmpp.Connection is really a module that breaks the
encapsulation that is Network.Xmpp and the concurrent interface, I
have renamed it Network.Xmpp.Internal. As this frees up the
Network.Xmpp.Connection name, Network.Xmpp.Connection_ can reclaim it.

The high-level "utility" functions of Network.Xmpp.Utilities,
Network.Xmpp.Presence, and Network.Xmpp.Message has been moved to
Network.Xmpp.Utilities. This module contains functions that at most
only depend on the internal Network.Xmpp.Types module, and doesn't
belong in any other module.

The functionality of Jid.hs was moved to Types.hs.

Moved some of the functions of Network.Xmpp.Pickle to
Network.Xmpp.Marshal, and removed the Network.Xmpp.Pickle module.

A module imports diagram corresponding to the one of my last patch
shows the new module structure. I also include a diagram showing
the `Sasl' and `Concurrent' module imports.
Join `Stream' and `Connection'

The `Stream' and the `Connection' modules/concepts has been quite
similar and, in some ways, overlapping. The `Stream' and `Connection'
modules allow for direct access to the XML stream. The `Stream' module
exported an API for opening, restarting, and closing the stream. The
`Connection' module, on the other hand, allowed for pushing and
pulling elements and stanzas to and from the stream. Furthermore, the
`Connection' type was used in both the `Connection' module and the
higher-level `Stream' module.

This patch joins the two modules into one `Stream' module, and renames
the `Connection' type to `Stream'. It also renames most other
connection-related functions and types. Also, `connect' is renamed
`openStream' and `closeStreams' is renamed `closeStream' (the stream
is `bidirectional' in RFC 6120 terminology).
Moved two stream-related pickler/unpickler's to Marshal
XEP modules depend only on `Network.Xmpp' and `Network.Xmpp.Internal'
Export functions necessary for external SASL handlers
Renamed some stream-related record fields

Prefixed the fields with `stream'. `ServerFeatures' was renamed
`StreamFeatures' to be more coherent with the terminology in RFC 6120.
Move Data.Conduit.Tls functions to the Network.Xmpp.Tls module
Clean-up and migration of Text.Xml.Conduit.Elements

`ppElements' is only used by Network.Xmpp.Xep.InbandRegistration, so I
moved it there for the time-being.

As `elements' is only used in Stream.hs, I moved it there.

`parseElement' is not used anywhere, and was removed completely.

`renderElement' (and its local `elementToEvents' function) is used by
Stream.hs and Concurrent.hs, so I moved it to Utilties.hs. (We could
argue for a separate `Elements' module, but right now that seems
a bit thin. `openElementToEvents' is used by both `elementToEvents'
and `renderOpenElement', so I put both `openElementToEvents' and
`renderOpenElement' in Utilities.hs as well.

`compressNodes' and `streamName' were made where-local to `elements'.

The types were moved to Types.hs.
Remove simpleAuth
Renamed pushIQ' to pushIQ

There is no longer any naming conflict.
Export StanzaID; rename StanzaId constructor
Moved `withStream', `withStream\'', and `mkStream' to Stream.hs
Remove SaslM

While short, I do believe that `SaslM' type makes the code
significantly less understandable. This is at least the case for me.
This patch removes it and changes the types to read the full `ErrorT
AuthFailure (StateT Stream IO) a' type instead.
Remove Pickle helpers from Network.Xmpp.Internal
Remove exports of the SASL helper functions

This patch removes the exports of the SASL helper functions of
`Network.Xmpp.Internal'. While these could be useful if someone were
to implement a `SaslHandler', the use of these functions would be
extremely uncommon, and I think that these functions would clutter the
API unnecessarily.
UNFINISHED Merge remote-tracking branch 'nejla/master'

Conflicts:
	source/Network/Xmpp/Concurrent/Types.hs
	source/Network/Xmpp/Connection_.hs
	source/Network/Xmpp/Internal.hs
	source/Network/Xmpp/Pickle.hs
	source/Network/Xmpp/Session.hs
	source/Network/Xmpp/Stream.hs
	source/Network/Xmpp/Types.hs
	source/Network/Xmpp/Xep/InbandRegistration.hs