- moved constants GRAVITY_* from boot.php to Friendica\Model\Item
- also rewrote some array initialization:
From:
````
<?php
$arr = [];
$arr['foo'] = "FOO";
````
To:
````
<?php
$arr['foo'] = "FOO";
````
- added a few type-hints
- Move HTTPInputData::process() into App::runFrontend()
- Pass $_REQUEST (including processed Input) to every Module method
- Delete $_POST parameters at Module post() calls because of $_REQUEST
- Add all dependencies, necessary to run the content (baseUrl, Arguments)
- Encapsulate all POST/GET/DELETE/PATCH/PUT methods as protected methods inside the BaseModule
- Return Module content ONLY per `BaseModule::run()` (including the Hook logic there as well)
