Added KeyChain property to AuthKeyNegotiator.
Fixed bug with incorrect container seqno checking.
RpcResultHandler: added support for IRpcError.
ResponseDispatcher: added exception catcher.
MTProtoConnection: removed redundant async/await.
MTProtoBuilderFacts: added test category.
MTProtoConnection: added MTProto Methods property.
Small reformat.
Added SessionHandler.
Moved schema methods.

Schema methods were moved to a file:
MtpSharpMTProto.SharpMTProto.Schema.MethodsImpl.Ex.cs.
Added logging info.
RequestsManager: added check for RPC.

Added tests for RequestsManager.
MessageSendingFlags: added 'RPC' value.
TcpTransport: added a disposable bits.
Updated version to 0.6. Updated README.
Merge branch 'develop'