Analysers should have an init or validate function that checks they are ok #248

Our ts-lint analyser relies upon 'typescript' being installed.
I'll bundle for now, but we really should have a init function on an analyser that can be called when setting up the array of analysers to run. In init the analyser can make sure it has everything it needs, else return an error message.
The runner can remove analysers from the list-to-run, that return an error message from init, and in turn, the cli can show why we are omitting an analyser from a run.