[dev] better error handling

[steve]

Here is a patch for horde/base.php (an error was not catched)

diff -w -b -r1.23 base.php
35c35,38
< $registry->pushApp('horde');
---
 > if (is_a($registry->pushApp('horde'), 'PEAR_Error')) {
 >     Horde::fatal(PEAR::raiseError('Horde is not correctly configured, 
impossible to load the configuration files.'), __FILE__, __LINE__, false);
 > 	exit;
 > }