LICENSE: add info about SPDX-License-Identifier usage and use it

Signed-off-by: Roger Meier <roger@bufferoverflow.ch>
Merge pull request #439 from bufferoverflow/spdx2

LICENSE: add info about SPDX-License-Identifier usage and use it
mysql test db autocreate
restore SPDX license
restore id and add tested DB version
Merge remote-tracking branch 'upstream/develop' into develop