Added Value method to get reflect.Value from underlying entities

[dlahoza]

This will be helpful for working with values received by Go functions added to the globals.

globals := map[string: interface{}{
  "f": func Something(v inteface{}){
    //v will be *GoMap type
  },
  "v": map[string]interface{},
}

starlark
f(v)

[dlahoza]

Added small fix to FromDict