Vanilla Web UI support

[itsgoingd]

• added Web UI support to the Vanilla integration
• new Clockwork::returnWeb api is used for serving the Web UI
  • on the first run the Web UI assets are installed into the configured public directory
  • the Clockwork App is linked in an iframe to work around relative asset URLs and with a javascript snippet overriding the metadata api path
• the Clockwork App was updated to allow overriding of the metadata api path via settings
• note, installed Web UI assets are not automatically updated

Example usage:

// clockwork-web.php

$clockwork = Clockwork\Support\Vanilla\Clockwork::init([
    'api' => '/clockwork.php?request=',
    'web' => [
        'enable' => true,
        'path' => __DIR__ . '/vendor/clockwork',
        'uri' => '/vendor/clockwork'
    ]
]);

$clockwork->returnWeb();

A PSR-7 application using a router:

$router->get('/clockwork', function ($request) {
    $clockwork = Clockwork\Support\Vanilla\Clockwork::init([
        'web' => [
            'enable' => true,
            'path' => __DIR__ . '/public/vendor/clockwork',
            'uri' => '/vendor/clockwork'
        ]
    ]);

    return $clockwork->usePsrMessage($request, new Response)->returnWeb();
}};