Allow for extensibility and separate logical components.

Fix state name.
Fix instance_xml, sla_xml.

As RFC says in http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.4:

403 Forbidden
(...) If the server does not wish to make this information available to the
client, the status code 404 (Not Found) can be used instead.

Prove that OPTIONS is header ignorant.
Prove that POST on instance require headers.

Allow to require any header.

Configure GET/POST on /instance to require application/json in Accept and
Content-Type headers.

It is not used by Vifib.

requestSoftwareInstance request exactly 7 arguments.

This reduce the load of the server

Merde...pushing too fast.

Dates on payments are not set by builder, so while playing in test set it.

Computer might not have access to it.

Use common responseSupport which adds all expected headers and supports
anonymous access, so OPTIONS can be simplified.