driver global refactoring [GH-75]
'error.rb': added new and deleted unused error messages.
Gemfile: plugin moved to 'plugins' group

.gitignore: modified to be developer-frendly
Merge branch 'develop' into feature/driver_refactor

* develop:
  alias 'check_guest_additions' fixed
Driver refactoring (minor)
'import' and 'export' action refactoring [GH-36]

- register/unregister template actios has been moved to 'import' and 'export'
- added interrupt handling
- 'generate_name' util was deprecated
'action/network': max adapters number is defined by driver
'action/export': multi-hdd compacting fixed
'driver/pd_9': 'read_bridged_interfaces' method fixed.
driver and unit-tests refactoring  [GH-75]
unit test for 'create_host_only_network' driver method
driver and unit-tests refactoring
'pd_8' and 'pd_9' drivers are separated from each other
Merge branch 'feature/driver_refactor' into develop

* feature/driver_refactor:
  'pd_8' and 'pd_9' drivers are separated from each other
  unit test for 'create_host_only_network' driver method
  driver and unit-tests refactoring  [GH-75]
  'driver/pd_9': 'read_bridged_interfaces' method fixed.
  'action/export': multi-hdd compacting fixed
  'action/network': max adapters number is defined by driver
  'import' and 'export' action refactoring [GH-36]
  'error.rb': added new and deleted unused error messages.
  Gemfile: plugin moved to 'plugins' group
  '.gitignore' was made developer-friendly