So far implementation of slapos proxy was incomplete regarding partition destructions:
A partition requested as destroyed was properly destroyed "physically", files were
removed from filesystem, services were removed from supervisor, but the partition was
still marked as busy in proxy database, so it was never re-used in subsequent requests.

To solve this, implement the destroyedComputerPartition endpoint to mark the partition
as free.

This is straightworfard for root partitions, but the cases of child partitions was a bit
more tricky, especially because software releases usually does not implement properly
the chain of deletion (it seems this is not properly implemted with softwaretype, only
with switch_softwaretype) and generally because we don't want to leave orpheans partitions.

In the case of ERP5 implementation of SlapOS master we have an alarm which garbage
collect in these cases, so we implement something to reach similar goals. We refuse freeing
a partition while their child paritions are not freed - and we request deletion of these
partitions so that they are deleted on next slapos node report run. Then after a few runs,
the whole partition tree will be completely destroyed and freed, even for software which
does not implement deletion properly.

This way, we can call methods interacting with master on the
returned partitions

Output is already captured on SlapPopen instances and the output
is available with output attribute.

    User can view his Cloud Contract and its consumption.

      This is used to Sales website when a Invitation token is provided and it will be used when request button will be available on logged user website.

    This consider Maximum Delay and Maximum Credit a user can have

   This is a faster version to later accomodate custom implementation from Cloud Contracts

    This help us to avoid query outdated catalog, consider that the user is only at transaction for now.

  This requires more work before continue.

See merge request nexedi/slapos.core!245

When test machine is busy it happens that running a simple promise takes more
than one second and this cause some test to error with "Promise timed out after
1 seconds" in cases where the promise is not supposed to have a timeout, it's
just that sometimes it takes more than the default timeout of 1 second.

   Cover the the update the update of allocation_scope
   Cover the Computer Network set Reference
   Cover the bootstrap of Project
   Cover setRole on Organisation

Helper function to return the configuration used by a promise plugin.

Helper class to check crontabs in software release tests

    This makes a direct edit w/o introspect previous value.

   We don't need to generate password everywhere