add tests to check that a Slave Instance will not be allocated when a Software Instance is destroyed

rename variable to be consistent with ComputerPartition.request and follow last changes in person_slap_interation_workflow

refactor code to the paremeters be consistent with ComputerPartition.request. Use shared and shared_xml instead of slave_xml

software_instance was not available anymore.

During finding root software instance not full tree is analysed. In order to
have more complete graph just add some nodes which shall be. They will be
mostly leaf nodes, so they do not impact graph connectivity nor cycleism.

add steps to validate the states of sale packing lists when exists many slave instances and is requested start/stop of all instances

change the parameter of "ERP5Site_getSlaveInstanceListFromComputerPartition" to be possible to pass parameters to catalog search

Root software instance requests shall be disallowed, period.

Graphs were not cyclic.

Moreover update existing tests in order to simulate real cases.

Even more -- return True in case if all was ok.

Instead of raising ValueError, which is used all the time, except
DisconnectedSoftwareTree exception.

It allows to have selective detection of software instance problem and allows
to test what exactly was told.

Treat tree of software instance as graph and simulate requested changes.
Before doing any real changes check if graph is still connected.

Add utility method to software instance class in order to use collections
module and have fast graph walking.