Make features scope dependent

Currently all features and configuration options are global. So if someone activates a special feature in a module, this will be activated during the complete run and not only for functions that are in this module.

For example:

Module "A":

package A;
use Rex -feature => ['1.0'];

Rexfile:

use Rex -feature => ['0.57'];
use A;

Now the feature profile "1.0" is acticated and some functions the Rexfile author depends on might not work as expected anymore. This is why every module should use use Rex -base.

To prevent this and to allow module authors to load features only in their modules we need to make (at least) the feature flags scope dependent.

Start by tracing how Rex feature flags and configuration options are loaded across modules and the Rexfile. Define the scoping behavior using the Module A and Rexfile example, then verify that each module's feature profile affects only functions in that module without changing the caller's profile.