Fix code styling offences throughout the project

# Problem

Through #499 and #593, we introduced `eslint` and `ember-suave`. The changes were made in a manner that the current state of the project stays green. Now it's time to improve styling, so we gotta attack each of the rules that have been turned off, fix them, and remove them off the list.

The full list is outlined below.
## Subtasks
- [x] no-unused-vars
- [x] one-var
- [x] generator-star-spacing
- [x] no-trailing-spaces
- [ ] comma-dangle
- [ ] spaced-comment
- [ ] object-shorthand
- [ ] quotes
- [ ] brace-style
- [ ] max-statements-per-line
- [ ] keyword-spacing
- [ ] no-var
- [ ] space-in-parens
- [ ] indent
- [ ] space-infix-ops
- [ ] operator-linebreak
- [ ] object-curly-spacing
- [ ] dot-notation
- [ ] no-console
- [ ] prefer-template
- [ ] space-before-function-paren
- [ ] comma-spacing
- [ ] no-multiple-empty-lines
- [ ] camelcase
- [x] key-spacing
- [ ] new-cap
- [ ] space-before-blocks
- [ ] ember-suave/no-const-outside-module-scope
- [ ] ember-suave/no-direct-property-access
- [ ] ember-suave/prefer-destructuring
- [ ] ember-suave/require-access-in-comments
- [ ] ember-suave/require-const-for-ember-properties
## How to fix
1. On the [ESLint file](https://github.com/code-corps/code-corps-ember/blob/develop/.eslintrc.js), remove any rule that you're interested in fixing.
2. This will lead to errors corresponding to offences on that rule.
3. Once you fix them, you may start a new PR

Let's get this going!

Beginne in .eslintrc.js, indem du eine nicht aktivierte Regel auswählst und sie aus der Konfiguration entfernst. Führe ESLint aus, um die daraus resultierenden Verstöße zu identifizieren, behebe die gemeldeten projektweiten Styling-Probleme und überprüfe, dass die Regel ohne Fehler aktiviert bleiben kann, bevor du einen fokussierten Pull Request eröffnest.

Vom Indexierungsmodell aus dem Issue-Text verfasst.