API calls for comments, spots, city projects, locations

[nicoverbruggen]

We need to add more API calls to api.php.

For example, when you add a comment, JSON is sent to /api/comments, which you can access using:

$app->post('/api/comments/', function () use ($app){
$requestBody = $app->request()->getBody();
// Do things
});

We need to do this for all major data types, and allow additions, edits, deletions and of course getting the data. Data should be returned in JSON.

Note that we need a partially working front-end with AJAX calls to test out the API.