Keep backward compatibility and start automatically just after partition become
available.

Implement start_requested and stop_requested states in order to have stateful
information about software instance requested state.

Asynchronously read software instance state and take proper actions in such
case (only after .available() call for now).

Note: Done in one big commit, as changes are interrelated, and impact system
functionality.

Make it not required, in order to support older versions of slap library.

Default to started, in order to support usual scenarios, when all is started
automatically.

Thanks to partially reverting "Use only externally provided buildout."
(commit 2a0bbcc9) it is possible to use
slapgrid with provided buildout binary, but no one is forced to follow this
way, as old style internal bootstraping procedure is available.

Conflicts, manually merged:

	slapos/grid/slapgrid.py
	slapos/grid/utils.py

Allow to have not defined buildout binary.

This functionnality is already provided by request.

Clean up the test because this tests and scripts were moved to erp5_credential. In testVifibCredential have only one test to validate if feature of subscription works in vifib context as expected.

Use by default checkUserCanChangePassword, but as in ERP5 users do not have
such persmission to Person document which defines them, check if logged in user
login is same as document reference.

Prove that user can request and revoke certificate for himself.
Prove that user cannot request twice the certificate.
Prove that user cannot request nor revoke certificate for another one.

Note: Currently failing, because users cannot set own passwords.

It allows to get/revoke certificates for Person. Protected in same way as setting Person's password.

This is too dangerous, as it allows to generate certificates for any user.

Try to confirm order related to another requested software instance. It shall
fail with ValueError, which indicates in Vifib, that no free partition was
found, which means that SLA was correctly used.

As there is no way to have returned object, generate random value and reuse it
later to fetch exact object.

Also extended tests with Order Line checks.

sla_xml have to be passed always. As this test have to work on low level API
it is required to follow such API.