there have been issues with filenames that include spaces or other
characters. this is solved by double URL encoding.

for details see the migration guide for v2.0.0:
https://github.com/bootstrap-vue/bootstrap-vue/releases/tag/v2.0.0

also uses a b-table instead of b-rows because they are easy to rerender
after changes to the playlist entries array

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

* 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