Comments every methods in every header

Now, there should be only an 'Enabled' toggle for each account. It determines
if the account is registered on start-up AND if it's enabled, generally.

TODO: We'll need another parameter, to select which account is the one used
to do calls. Anyways, it wasn't very convenient to use the 'First one enabled',
since you'll often want multiple accounts enabled, and be able to select which
account to use for an outgoing call.

This commit updates the SFLphone daemon and the Gtk+ client.

It removes a whole bunch of useless variables (_state, _shouldInitOnStart,
_shouldRegisterOnStart, _registered). Now the registration state is fetched
directly from the VoIPLink (when called from the Account). So, no more
duplication of statuses.

TODO: SFLphone-gtk will need to support the TRYING and ERROR messages as
'Status' reply.

* Renamed setRegister/setUnregister to sendRegister/sendUnregister, reflecting
  more precisely what the function does.
* Renamed (un)registerAccount to (un)registerVoIPLink in account/iaxaccount/sipaccount
* Renamed (un)registerVoIPLink to (un)registerAccount in managerimpl.cpp|h
* Prepared the way for dynamic registration reporting (to the GUI). Now has
  more precise way to describe reg. state: Unregistered, Trying, Error, Registered
* Delete `_link` on SIPAccount/IAXAccount destruction
* All sync of the regist. state with the Manager, is now done in
  VoIPLink::setRegistrationState()
* Document all the way

Tiny doc fixes and typos.

Working DBus

Documentation generation (remove copyright as doxygen brief summary)
doygen Doxyfile

New account implementation.
Need to test more and add dynamic handling in Qt Interface.
SipCall, Call, VoIPLink were rewritten completly
Configuration now in [SIP0] section of .sflphonedrc
The debug of sflphoned is very verbose.
sflphone-cli may not work right now (need to send SIP0 as accountId).

First Account-based save/load implementation

Add AccountCreator and AccountMap handling
New empty AixAccount/SipAccount
Next step is internal account configuration

Zeroconf integration