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/t-users/users.inc.php

@@ -0,0 +1,43 @@
+<?php
+
+
+class Dao_Users
+	extends DAO
+{
+	private function hashPassword( $password , $salt , $iterations )
+	{
+		$hash = $password;
+		$salt = trim( $salt );
+		do {
+			$hash = sha1( "$salt$hash$salt" );
+			$iterations --;
+		} while ( $iterations > 0 );
+		return $hash;
+	}
+
+
+	public function getUser( $email )
+	{
+		$query = $this->query( 'SELECT * FROM users WHERE user_email = LOWER( $1 )' );
+		$results = $query->execute( $email );
+		if ( empty( $results ) ) {
+			return null;
+		}
+		return array_shift( $results );
+	}
+
+
+	public function checkLogin( $email , $password )
+	{
+		$userData = $this->getUser( $email );
+		if ( $userData != null ) {
+			$hashed = $this->hashPassword( $password ,
+				$userData->user_salt ,
+				$userData->user_iterations );
+			if ( $hashed === $userData->user_hash ) {
+				return $userData;
+			}
+		}
+		return null;
+	}
+}