Added more code and unit tests for ConnectionObject & FakeConnectionObject

Added more code and unit tests for ConnectionObject & FakeConnectionObject

Added code and unit tests for the following functions in the
ConnectionObject interface (and FakeConnectionObject class):

EditContact(std::string, std::string);
DeleteContact(std::string, std::string);
GetServerEntityTagValue(std::string);
GetContact(std::string);
GetContactList(std::string);