Use correct SPDX license specification in appdata
Use correct SPDX license specification in appdata

Translate license names to their SPDX equivalents and separate with
the AND syntax, as detailed at:

 * https://spdx.org/spdx-specification-21-web-version
 * https://spdx.org/licenses/

AlanJAS/turtleart,walterbender/turtleart