doc: added a note to logicalfile

Explained a goal of this provider.
doc: add some info to power management script

Mentioned that machine cannot be powered on for obvious reasons.
sw: lot of fixes and improvements

* tuned connection timeout for several commands

  Software operations take a long time in general. 1 second timeout (the
  default for lmiwbem) is too short. Extend it for chosen commands.

* support sw provider with packagekit backend
* Speeded up enumeration of all packages at the cost of disposing of
  additional columns.
* Fixed usage string of *list* command. Its *all* subcommand cannot be
  optional.
* Use the quieckest possible method to determine whether package is
  installed for both providers.
* Better described search command.
* Speeded up check for an installed package.
* Fixed an error caused by logging message after successful package
  installation.
* Added support for Installed parameter of FindIdentity
* Enhanced *sw search* searched command with new
 (--installed | --available) options.
* Warned about slowness of sw provider in docs.
* Added support for repoid parameter in queries.
* Provide some useful error description for async methods.
hardware: optimize query for disk information

Be specific when requesting associators for disk drive. With many
providers installed on managed machine, the query may become quite slow
because of enumeration of many association classes.
system: optimized network info gathering

Specified association class name in a query to broker to speed it up.
journald: fixed watch command

LMIListener's start method no longer returns any value - do not check
it.