Make Rakefile work with RSpec 3.1

RakeTask in RSpec 3.1 does no longer allow to specify an array of paths
as the pattern. Since the purpose of the problematic rake task is only
to exclude the integration test we use the new "exclude_pattern" method
to achieve the same result instead.
Merge pull request #187 from SUSE/review_140905_fix_rakefile_in_rspec_3_1

Make Rakefile work with RSpec 3.1
Remove obsoleted nil checks as due to the json validation these not
necessary anymore.
Merge pull request #179 from SUSE/review_140903_remove_obsolete_nil_checks

Remove obsoleted nil checks as we now can validate based on the schemas defined.
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.
Implement method to clean up json error messages

Implement testable method to clean up the weird json error messages
since they are unusable for some scopes like unmanaged-files.
Use cleanup_json_error_message for json validation error handling