The `/etc/issue` file should be generated instead of updated for every new version

[pawosm-arm]

Currently, Standalone/filesystem-src/etc-files/issue looks like this:

 ^ ^
 n n   Fuzix 0.3.1
 >@<
       Welcome to Fuzix
 m m

The version number was not updated for a while and from git log I can see that it needs to be updated manually. IMO a better idea would be to turn it into a template (e.g. issue.in) and generate /etc/issue file at the build time with the actual version number.