Remove superfluous string preparation calls for scrubbing

The "dup" and "force_encoding" calls were extracted into the "scrub"
method in c36fd7470 and are thus not necessary here anymore.
Schemas: Remove duplication

Remove duplicate property schemas in schemas for "config_files" and
"changed_managed_files" scopes.
Schemas: More precise descriptions of file states

In case of "config_files" and "changed_managed_files" scopes, there are
two possible states of each file:

  1. The file was changed ("status": "changed")

     This state has two sub-states:

     1.1 The file was modified ("changes": [...]).

         In this case, the list of changes is saved in the "changes"
         attribute and file metadata is saved in the "mode", "user" and
         "group" attributes.

     1.2 The file was deleted ("changes": ["deleted"]).

         In this case, no metadata is saved.

  2. Determining whether the file was changed resulted in an error
     ("status": "error").

     In this case, the error message is saved in the "error_message"
     attribute.

This commit modifies schemas for "config_files" and
"changed_managed_files" scopes to match the states correctly.
Merge pull request #183 from SUSE/review_140904_remove_superfluous_string_preparation_calls_for_scrubbing

Remove superfluous string preparation calls for scrubbing
Merge pull request #184 from SUSE/schema-config-files-changed-managed-files-more-tweaks

[Review] Request from 'dmajda' @ 'SUSE/machinery/schema-config-files-changed-managed-files-more-tweaks'
Use SystemDescriptionStore to load validation file

Showing the file path requires the SystemDescriptionStore object
to check the real error message.

Removed unnecessary unit test due to other tests validates this.

Moved the validation files to keep uniform direcory layout.

Moved validation tests from system_description_spec to
system_description_validation_spec.
Consolidate integration validation descriptions with unit tests

Moved the integration invalid-json and validation-errors into
subdirectorys to have the same layout as the unit tests.
Add file path to validation error message
Move validate task descriptions to common directory
Adapt error messages and tests to new schema

The config- and changed-managed-files schema was changed in an similar
way as the unmanaged-files inspector so the error messages have
changed.

The regex did not apply anymore so we removed it.