Provide "off-rails" runtime coverage recording

Allow users to instruct instrumented applications to write coverage even if the .db is not available at runtime

New system property:
clover.offrails.coverage=true|false (default: false)

A value of true makes Clover ignore when, at runtime, it can't find the instrumentation database pointed to by the initstring (as at build time or overridden via system properties) and will writes coverage to this location anyway. It will create any folders that need to be created and will currently throw an IOException if they can't be created.

A value of false or an absent value will make Clover record no coverage (with an appropriate warnings). No AIOOBEs should be generated anymore for applications with # elements > the fictitious maximum we originally concocted.