Move functionality from static start and destroy functions into instance
methods, allowing these to be overloaded. This works the same way as
calling Session::set() which then in turn calls inst_set()
Additionally use Injector to create the default Session instance to
allow the class to be swapped out.
The entire framework repo (with the exception of system-generated files) has been amended to respect the 120c line-length limit. This is in preparation for the enforcement of this rule with PHP_CodeSniffer.
