dev: Use shared_ptr for Arguments::Data

dev: Use shared_ptr for Arguments::Data

This patch takes a first few steps in transitioning from the ad-hoc
RefCountingPtr to the c++11 shared_ptr. There are no changes in
behaviour, and the code modifications are mainly introducing the
use of make_shared.

Note that the class could use unique_ptr rather than shared_ptr, was
it not for the postfix increment and decrement operators.