Fix if statement
Add pro version tag and function for checking for pro version
Add post-checkout git hook script
Add Methcla::Version::isPro predicate
Add stub for disksampler plugin

This is needed for determining which plugin to use at runtime in
the non-pro version of methcla.
Use sampler or disksampler depending on methcla version
Make use of sampler plugin configurable at runtime in sampler example
Code formatting