Replace existing autoloader with Composer-supplied

- Move Friendica namespace to `src`
- Move required `ezyang/htmlpurifier` to vendor
- Remove existing static autoloader
- Change boot.php reference to the autoloader

vendor/ezyang/htmlpurifier/library/HTMLPurifier/ConfigSchema/schema/HTML.SafeObject.txt

@@ -0,0 +1,13 @@
+HTML.SafeObject
+TYPE: bool
+VERSION: 3.1.1
+DEFAULT: false
+--DESCRIPTION--
+<p>
+    Whether or not to permit object tags in documents, with a number of extra
+    security features added to prevent script execution. This is similar to
+    what websites like MySpace do to object tags.  You should also enable
+    %Output.FlashCompat in order to generate Internet Explorer
+    compatibility code for your object tags.
+</p>
+--# vim: et sw=4 sts=4