Update Debian config to match current (buster/bullseye) standards

[maxberger]

• bump compat level 13
• add needed dependencies in control
• Updated init with proper path
• Added service file
• Fix postint to create conf file if not present

[r00t-]

@maxberger: sadly no debian packaging experts on our team. could you also have a look at https://github.com/volkszaehler/libsml/pull/97 ?

[maxberger]

@maxberger: sadly no debian packaging experts on our team. could you also have a look at volkszaehler/libsml#97 ?

Unfortunately I am not a debian expert, so I am not the right person to look at this related Pull request.

[maxberger]

While I totally agree that rewriting the .service file to use foreground makes sense, I really just took the example file from the main directory and copied it to debian/ to make this work with the current dh-build. If you want to change the .service file, this is a different dicscussion, and should be done in a different PR.