Merge pull request #16 from iwoloschin/master

Modified Enable Commands For Rigol
Minor bug fix in _set_output_enabled
Rework PropertyCollection
Add IviContainer object as ultimate base class
Fix docs and default values for instrument identity parameters
Convert base classes to use IviContainer
Update ivi extra base classes to use IviContainer
Update scpi dcpwr for consistent naming
Update scpi dmm to use default scpi implementations
Rename initialize to _initialize
Use self._add_method/property instead of ivi.add_method/property
Convert top-level methods and properties to use _add_property/method
Use %f instead of %e for better compatibility
Use dicts for index lookup for improved performance
Raise correct exception
Implement __iter__ for IndexedPropertyCollection
Access index as a named parameter from IndexedPropertyCollection
Access value as a named argument from PropertyCollection
Merge pull request #1 from python-ivi/master

Update