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!

Inizia in .eslintrc.js scegliendo una regola non selezionata e rimuovendola dalla configurazione. Esegui ESLint per identificare le violazioni risultanti, correggi i problemi di stile segnalati in tutto il progetto e verifica che la regola possa rimanere abilitata senza errori prima di aprire una pull request mirata.

Scritto dal modello di indicizzazione a partire dal testo della issue.