Rewrite:

- 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

src/Module/Update/Network.php

@@ -23,6 +23,7 @@ namespace Friendica\Module\Update;
 
 use Friendica\Core\System;
 use Friendica\DI;
+use Friendica\Model\Item;
 use Friendica\Model\Post;
 use Friendica\Module\Conversation\Network as NetworkModule;
 
@@ -55,7 +56,7 @@ class Network extends NetworkModule
 			} elseif (self::$order === 'received') {
 				// Only load new toplevel posts
 				$conditionFields['unseen'] = true;
-				$conditionFields['gravity'] = GRAVITY_PARENT;
+				$conditionFields['gravity'] = Item::GRAVITY_PARENT;
 			} else {
 				// Load all unseen items
 				$conditionFields['unseen'] = true;

src/Module/Update/Profile.php

@@ -72,7 +72,7 @@ class Profile extends BaseModule
 
 		$condition = ["`uid` = ? AND NOT `contact-blocked` AND NOT `contact-pending`
 				AND `visible` AND (NOT `deleted` OR `gravity` = ?)
-				AND `wall` " . $sql_extra, $a->getProfileOwner(), GRAVITY_ACTIVITY];
+				AND `wall` " . $sql_extra, $a->getProfileOwner(), Item::GRAVITY_ACTIVITY];
 
 		if ($_GET['force'] && !empty($_GET['item'])) {
 			// When the parent is provided, we only fetch this