Load functions embedded in modules

[tuckermcclure]

Writing a function to a YAML will look like this:

my_function_wrapper:
    type: FunctionWrapper
    fcn: Main.ModuleA.ModuleB.foo

Those can then be loaded in correctly.

Note that this has nothing to do with running a function (when the type to load is in fact a Function and not a Type{Function}). When the type is Function, the syntax is "run the function with the given keyword arguments". When loading Type{Function}, the function itself is what is returned.

Obviously, anonymous functions don't work, and we check for that explicitly.