Force user to select a sample

This has the side effect of blocking all context changes until the sample is selected but that is necessary given the way required concepts are implemented currently in Cilantro. There is a notification made to the user when they try to modify the context with no sample selected so it should be clear enough that no one is confused.
Update Cilantro to 2.2.11
Fix custom controls config options to match changes in Cilantro 2.2.11
Notify user on both CONTEXT_REQUIRED and _INVALID events

This was not working pre Cilantro 2.2.11 because CONTEXT_REQUIRED did not supply the correct argument to handlers.
Merge pull request #112 from cbmi/issue-64

Force user to select a sample