requestSoftwareInstance requires much less arguments.

Expose tool which is capable to reply to low level HTTP requests (like POST,
DELETE, PUT).

Caller uses catalog to call method, avoid trusting it.

This replace the previous root_state property defined on Hosting Subscription.

Stay consistent with current API

This simplify retrieval of this information (and so, reduce system load).

Do not set any default value anymore.
This should ease compatibility issue (less maintainance).

Generally allow customer to repay payment. The work was based on:

 * Start date do not have to be set during building.
 * Allow to reuse existing ID and allow PayZen to inform user, that transaction
   is already registered.
 * Do not create too many ids.
 * Drop not needed logging.
 * Be as precise as invoice's currency.
 * Consider all planned or confirmed transactions and take actions based on
   transaction status.

Do not kill the client browser.

Sleep is bad, but better than destroying all components.

It is only used in vifib_web

This will ease maintainance.