Reworked handling of error-responses from the Graph-API
* The parsing of the response is done by the ObjectMapper from Jackson.
* Unmapped exceptions are returned as such, instead of handing the handling
to the parent.
- [DH] src/main/java/de/juplo/facebook/client/GraphApiErrorHandler.java
- [DH] src/main/java/de/juplo/facebook/exceptions/GraphApiException.java
- [DH] src/main/java/de/juplo/facebook/exceptions/GraphApiExceptionJackson1Deserializer.java
- [DH] src/main/java/de/juplo/facebook/exceptions/GraphApiExceptionJackson2Deserializer.java
- [DH] src/main/java/de/juplo/facebook/exceptions/GraphMethodException.java
- [DH] src/main/java/de/juplo/facebook/exceptions/OAuthException.java
- [DH] src/main/java/de/juplo/facebook/exceptions/PageMigratedException.java
- [DH] src/main/java/de/juplo/facebook/exceptions/RateExceededException.java
- [DH] src/main/java/de/juplo/facebook/exceptions/UnexpectedErrorException.java
- [DH] src/main/java/de/juplo/facebook/exceptions/UnknownErrorException.java
- [DH] src/main/java/de/juplo/facebook/exceptions/UnmappedErrorException.java
- [DH] src/main/java/de/juplo/facebook/exceptions/UnsupportedGetRequestException.java
- [DH] src/test/java/de/juplo/facebook/client/GraphApiErrorHandlerTest.java
- [DH] src/test/java/de/juplo/facebook/exceptions/FacebookErrorMessageMappingTest.java