api: fix 'projects' endpoint, don't paginate, always return JSON

Fixes monero-site#689 (closed)

Updated projects JSON API endpoint. Will be available at https://ccs.getmonero.org/index.php/projects

Returns all FUNDING-REQUIRED, WORK-IN-PROGRESS and COMPLETED projects.

{
    "data":
    [
        {
            "address": <address>,
            "author": <author>,
            "contributions": <contributions>,
            "date": <date>,
            "percentage_funded": <percentage_funded>,
            "raised_amount": <raised_amount>,
            "state": <state>,
            "target_amount": <target_amount>,
            "title": <title>
        },
        ...
    ]
}