New linter rules:
* curly
* block-spacing
* keyword-spacing

Also apply all autofixes introduced by these rules

Our linting config in package.json was:
```
    "extends": [
      "plugin:vue/essential",
      "eslint:recommended"
    ],
```

Now switching to "plugin:vue/recommended" and apply all auto-fixes

this is syntactically more correct.
also the linter does not complain anymore now :)

* facilitate new bootstrap-vue table features to get rid of computed table array
* use template slots of the b-table for better rendering
* button group for edit and delete
* implement delete function

* add filesize npm package
* add prettyNanoseconds mixin function

now displaying files and playlists in a b-table or asking to upload something

also refactored groups to shows, after tank refactoring happened

does not work yet, we always get back a 400 when
logo or image are not null in json format

have to find out how the exact format and encoding has to be to update
a show inlcuding files