Fix for Bug 489.

Fix for Bug 489.

Current code generator version was unable to generate sources for augmentation defined under uses statement
if augment points to nested node (not top level node added by uses).

Failing example:

container c {
    uses route-subobjects {
        augment "links/link" {
            leaf id {
                type string;
            }
        }
    }
}

AugmentationSchemaBuilderImpl: fixed bug in parsing augment target path for augmentations defined under uses.
BindingGeneratorImpl: fixed resolving of augment package name.
BindingGeneratorUtil: added new method to generate package name.

Added tests.

Change-Id: Ie48b2fffc0e6449bf5c13b5a6b636cbd837ffb54
Signed-off-by: Martin Vitez <mvitez@cisco.com>