Update brushes directory structure and file names.
- Previously, brushes were stored directly under a Corporate
directory. When this branch is merged with tcar branch brushes were
stored under the same directory which poorly describes its content.
To be more specific, this update creates the Brushes/Corporate
directory structure for storing brushes, instead of just Corporate.
- Previously, brushes were using the name symbol for both gbr and xcf.
In order to be more specific, this update changes the file name of
brushes from symbol.gbr to centos-symbol-48x48.gbr and from
symbol.xcf to centos-symbol.xcf.