Added phpdoc on all getters

This simplifies the usage of the SDK by allowing IDEs to provide autocompletion rather than having unknown types everywhere.

I also added the array initialization of array properties, to ensure that they are always arrays even if the serializer does not set them for some reason (the incomplete Analysis returned in ``getAnalysisStatus`` for instance).
@lyrixx there is actually an inconsistency here. the setter expects receiving one of the TYPE_* constants, which are integers. And the type returned in the XML looks like an integer. However, the serializer metadata are defining the type as ``@Type("string")``, which means that using a struct comparison between the data returned by the API and the constants will fail.