Drop "rc" for release candidates in version & replace with release commit hash

[rootzoll]

The idea is that when the final published release candidate sd card image is all good - there is no need to rebuild the sd card image just to change the version version string. This cuts a lot of time needed for building & testing - just rename the file to final release and all is ready.

To detect if user is still running a release candidate on support requests - the short commit hash of the raspiblitz repo used on running release (last step in building the sd card image) is displayed on LCD and in debug reports.