[SIP SIMPLE client] Addition to sip-settings page

[Adriaan de Groot]

On http://sipsimpleclient.com/wiki/sip_settings, please add the following at 
the bottom:

You can make an account the default account for outgoing calls with

	sip-settings -a default user at domain

Individual settings for the account can be set with 

	sip-settings -a set user at domain key=value

To see which settings are available, use

	sip-settings -a show

The settings are organized in a hierarchy. Use dotted notation for the keys. 
For instance, the outbound_proxy setting in the sip group is written 
sip.outbound_proxy. Use the dotted form in the command-line:

	sip-settings -a set user at domain sip,outbound_proxy=proxy.sipthor.net

Global settings are arranged the same way; for instance, to change the global 
outbound ringtone:

	sip-settings -g set sounds.audio_outbound=/path/to/wav