Removed individual options (intro* and startcenter* + images) in favor of a folder with graceful fallback.
Grouped progress bar intro settings in a text file into the branding folder

Change-Id: Ib56b80e43c474a944ac79c0a842d66487e9f91d5
Reviewed-on: https://gerrit.libreoffice.org/1704Reviewed-by: Petr Mladek <pmladek@suse.cz>
Tested-by: Petr Mladek <pmladek@suse.cz>