* [generator] Teach generator about WrapAttribute on Getters and Setters
https://bugzilla.xamarin.com/show_bug.cgi?id=57870
`WrapAttribute` can now be used in property getters and setters,
this allows to Wrap virtually anything the way you need, for example
smart enums, consider the following API definition:
```csharp
// Smart enum.
enum PersonRelationship {
[Field (null)]
None,
[Field ("FMFather", "__Internal")]
Father,
[Field ("FMMother", "__Internal")]
Mother
}
```
```csharp
// Property definition.
[Export ("presenceType")]
NSString _PresenceType { get; set; }
PersonRelationship PresenceType {
[Wrap ("PersonRelationshipExtensions.GetValue (_PresenceType)")]
get;
[Wrap ("_PresenceType = value.GetConstant ()")]
set;
}
```
* Fix Feedback
* Fix doc error
* Update error message
Alex Soto