Module call_history

Code to handle Call History data storage and display.

The format of the Call History is standardized.  It is an object with the
following attributes:

folder: string (where this item belongs)
datetime: string 'YYYYMMDDThhmmss' or (y,m,d,h,m,s)
number: string (the phone number of this call)
name: string (optional name associated with this number)
duration: int (optional duration of the call in minutes)

To implement Call History feature for a phone module:

  Add an entry into Profile._supportedsyncs:
  ('call_history', 'read', None),

  Implement the following method in your Phone class:
  def getcallhistory(self, result, merge):
     ...
     return result

The result dict key is 'call_history'.