[VPTOOL] Clean up documentation and code. Update copyright notice.

Created by: zchamski

Files changed:

• tools/vptool/VPTOOL-readme.txt (Configuration): Fix typo. (Directory structure): Fix names and descriptions of dirs/files. (Basic use): Fix incorrect paths.
• tools/vptool/vptool/vptool.yml (toplevel): Update copyright holder name. Refer to license text using SPDX identifier. (gui.title): Remove comment with a site-dependent list of themes.

Signed-off-by: Zbigniew Chamski zbigniew.chamski@thalesgroup.com @JeanRochCoulon @ASintzoff, please review.