Add Document::create() which creates a document with an object ID

[thekid]

Implements feature suggested in #47

use com\mongodb\Document;

// Creates a document without object ID
$chat= new Document(['topic' => 'Test', 'owner' => $identity]);

// Creates a document with a new object ID
$chat= Document::create(['topic' => 'Test', 'owner' => $identity]);

// Creates a (shallow) copy of the given document, assigning a new object ID
$copy= Document::create($chat);

[thekid]

Released in https://github.com/xp-forge/mongodb/releases/tag/v3.3.0