Add new properties for @JsonIgnoreProperties, "allowGetters", "allowSetters"

[cowtowncoder]

(note: to support FasterXML/jackson-databind#95)

Currently @JsonIgnoreProperties affects both serialization and deserialization, and it is not possible to support a relatively common use-case of "read-only" properties; ones that are output when serializing, but that are to be ignored upon deserialization (not requiring a setter).
One way to allow this is to add a new property, enabling of which will NOT ignore named properties during serialization.

Note that adding matching "allowSetters" is easy as well, so let's add that since the reverse use case seems plausible as well.