Added a new action GetKeys(preferenceName) to retrieve the keys for a specific preference set. 

PreferenceName  is an option parameter, if empty retrieves the keys from the default preference set.

Added support for 

* More than one set of preferences. All the methods have an optional parameter PreferenceName. If empty will refer to Default preference set. 

GET

• GetText
• GetBoolean
• GetInteger
• GetLongInteger

SET

• PutText
• PutBoolean
• PutInteger
• PutLongInteger

CHECK

• CheckSharedPreferencesPlugin
• HasKey

DELETE

• DeleteKey
• Clear