Protect option configuration from breaking handlers

[kumar303]

In #39 I protected command handlers from accessing undeclared program options. However, it is still possible to add an option to the program and forget to declare it (in ProgramOptions). This could result in handler unit tests that silently fail because they are testing with stale options. Let's see if we can solve it without resorting to a slow integration test. Perhaps it can be solved with static analysis.

[kumar303]

Adding strong typing may solve this. See #1144