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.