#146 Add mapi.HrSetOneProp() and mapi.HrGetOneProp()

[Nick Czeczulin]

This patch adds HrGetOneProp() and HrSetOneProp()

Mostly convenience functions that simplify the need to explicitly check for property errors when fetching/setting single properties.

In addition, HrGetOneProp() will also raise an error for properties that currently cannot be mapped using PyMAPIObject_FromSPropValue() since we are only dealing with a single value.

[Mark Hammond]

Thanks - f04eba3e2adb