Added Configurable setting to allow user to choose where to get the Donor's Address

* Add a Config Prameter called: 'Contribution Details Source'.
* Possible values are: 'DECLARATION' or 'CONTRIBUTION'.
* Default value is 'DECLARATION'.
* Modify the code to get the Contribution details depending on the new
Config Parameter.
Trap exception when Address cannot be located

... so that we can later ignore the record if required.
Merged master fixed conflict
Merge pull request #11 from longveda/Add-Config-Parameter-'Contribution-Details-Source'

Add config parameter 'contribution details source'