Remove obsolete mkdir creation in autoyast

The dir is already created in the task.
List scopes more natural with a space after comma

Fixes #356
Restrict the exported Autoyast directory to the user

As we discussed we don't want the exported directory to be
readable for all.
Provide note about Autoyast export permissions

Also add information to the readme how to change the permission.
Merge pull request #444 from SUSE/make_autoyast_export_private

Make autoyast export private
Adapt NEWS file to actual sprint 28 status
Merge pull request #445 from SUSE/update_news_file_sprint_28_3

Adapt NEWS file to actual sprint 28 status
Implement backup helper for SystemDescriptionStore

This method creates a full backup from a given system description and
returns the new name. If a system description already has a backup then
the new backup gets a number at the end.
Merge pull request #447 from SUSE/implement_backup_helper

Implement backup helper for SystemDescriptionStore
Implement rename helper for SystemDescriptionStore
Merge pull request #448 from SUSE/implement_rename_helper

Implement rename helper for SystemDescriptionStore
Merge pull request #443 from SUSE/fix_issue_356

List scopes more natural with a space after comma
Add tracking bug to RPM changes
Use GH tags for Github issues to be compliant

https://en.opensuse.org/openSUSE:Packaging_Patches_guidelines#Patch_naming
Add newly fixed bugs
Replace British version by American
Fix AutoYaST export readme
Merge pull request #452 from SUSE/fix_autoyast_readme

Fix AutoYaST export readme
Merge pull request #450 from SUSE/update_news_file_sprint_28_1001

Update news file sprint 28 1001
Move scope file store handling to own class

Move the methods dealing with the scope specific file store to
the ScopeFileStore class. Keep the methods in SystemDescriptionStore
for now and forward to the new class. They will likely be removed
in a later commit.