SLA XML is stored on Software Instance, but in many place the dictionary have
to be used.

It will be later used to follow SLA.

Later is shall be used in order to being followed.

It is easier to store on higher level, as pure XML. Other methods will have to
unserialise data from XML, which would be needed anyway in case of storing
them this way.

This reverts commit 79f0aaea.

More code analysis is required in order to being able support required cases
with parameters passed by user.

SlapTool itself shall not force to pass all possible parameters, as slap
library calls it in different ways.

Add support for lack of existence of computer_id and computer_partition_id,
in this case assume that human (person) is logged in by slap library.

Person does not have to be validated to be loggable user,
but Computer or Software Instance validation state is important,
so split to two queries.

Note: No typo in exception.

Two different scenarios are checked, for each start and destroy:

 * two different transactions, so activity tag is used
 * same transaction, so serialize blocking call is called

Whenever software instance is begin started or destroyed new packing list have
to be created. But in both cases it is not desirable to have more then one
active packing list related to current step of state. So dissallow it by
passing tag and checking for its existence. Even more -- serialize in order to
lock operation on one Software Instance in transaction.

Prepend with / in case of not matching in subdirectories.
Append with / in case of directories.

Use socket/time timeouts in small loops to react on common usage cases.
Be sure that supervisord is functional enough in order to avoid running other
steps in case of deconfigured svc backend.

Currently slap library was coded with optimistic assumption, that remote system
are not failing. But in order not to block library caller it is required to
setup timeout on socket operations, with default different than infinity.

It is nice to have python with all slapos.core modules.

While requesting Software Instance allow to edit instance XML, leave current
default in user interface.

While navigating to Software Instance make text_content editable and allow to
edit the form.

Include a specific script for additional configuration specific to the vifib project. Each additional configuration should be reviewed and recoded as Configurator Item on ERP5Configurator.

It is important to have in mind in this case that not always such configuration s should be converted in a generic setup.