Updated copyright of Krusader Krew in standard GPL headers
Updated GPL headers according to the latest standards
See [https://www.gnu.org/licenses/gpl-howto.html].
Replaced old license headers with fresh GPL headers
Fixed broken author names or emails
Updated and improved credits in supplemental files
Updated credits in the About dialog
Updated credits in docbook
Updated and standardized FDL license headers
Updated copyright years and release info in docs