Check for kernel debugging capabilities

[jtpio]

We should check whether a kernel has debugging capabilities or not before starting the debugger.

Related TODO:

debugger/src/service.ts

Lines 28 to 29 in f641270

	// TODO: also checks that the notebook or console
	// runs a kernel with debugging ability

There is a PR to add the debugger flag for kernel_info_reply in jupyter_client: jupyter/jupyter_client#486

In the meantime we can create an interface that extends IInfoReply and adds the debugger flag.

[jtpio]

We can start by adding that to the interface and to the tests.