SDK test: added testOriginalDictionary to make sure that properties added by the SDK do not leak in the result of [MXEvent originalDictionary]
SDK test: added testOriginalDictionary to make sure that properties added by the SDK do not leak in the result of [MXEvent originalDictionary]

matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk,matrix-org/matrix-ios-sdk