Implement major instrument locker function

[tribeiro]

One of the things that worries me most nowadays is that there is no way (that I am aware of) to guarantee no one can operate a certain instrument in certain conditions. For instance, let's say humidity is 100% or even that it is raining. I want to make sure no one (or nothing) accidentally try to open the dome.

One way around this would be to implement a "locker" function on ChimeraObject base class that simply locks the instrument until it is released.