+ Added some handy extensions for string:  AsGuid, AsDecimal, AsDateTime
+ Changed ConvertToEnum string extension to have an optional parameter "defaultValue". This helps us in situations where we would rather use a default enum value instead of raising an exception when the enumstring can't be parsed.
Updated references to ConvertToEnum to take advantage of the new "defaultValue" parameter in cases where the code wanted to use a defaultValue when parsing failed.
GivingAmountFilter is functional.  Still needs a little more testing.