Change use of raw new to std::unique_ptr and fix a shutdown race condition discovered using atomics.
Revert back use of std::unique_ptr on QTimer - QT manages the lifecycle.
Merge branch 'newtouniqueptr' of https://github.com/danielhams/cpp-ethereum into danielhams-newtouniqueptr

Conflicts:
	libethereum/Client.cpp
	libethereum/Client.h