Initial import of tasks application

This initial import is a heavily modified version of the code I had
here, as Arse was modified for other purposes in the meantime and the
application no longer worked with it.

In addition:
 * I did not import the user management part yet,
 * task dependencies are supported in-base, but there is no interface
for that yet.

includes/config-sample.inc.php

@@ -0,0 +1,7 @@
+<?php
+
+$config[ 'core' ][ 'db' ][ 'name' ] = '...';
+$config[ 'core' ][ 'db' ][ 'user' ] = '...';
+$config[ 'core' ][ 'db' ][ 'password' ] = '...';
+
+$config[ 'core' ][ 'pages' ][ 'baseTitle' ] = 'Tasks';