API - Basic API calls

This function should become something like this:

```php
    function get($category_id) {
        $sqlClause = create_SQL_clause(FOR_WHERE, array("cat_id" => $category_id));

        api_backbone((object)array(
            "request_type" => HTTP_GET,
            "access_level" => TOKEN_ACCESS_LEVEL,
            "query" => "SELECT cat_id, cat_name, cat_parent, theme FROM %scourse_cats" + $sqlClause,
            "queryArray"  => array(TABLE_PREFIX),
            "queryIDExistence" => "SELECT COUNT(*) FROM %scourse_cats" + $sqlClause,
            "queryIDExistenceArray" => array(TABLE_PREFIX)
        ));
    }
```