Multilanguage Support via gettext

- added gettext encapsulations to all texts i thought necessary
- added fallback function for the case that the gettext extension isn't loaded
- added browser language detection
- added gettext to the list of optional extensions in setup
- rewritten some of the texts to use sprintf instead of appending strings
- added german translation file
- removed mark_overdue-confirm from cannedresponses.inc.php

extend multi language support and a fex fixes

- Better detection of translation files
- Added functionality to redirect language codes (see redirecting
language codes)
- Ticket Status can be translated
- The Datepicker can be translated
- Extended functionality of 'testlang.php' to show what language code is
used to translate

Forgotten to apply a patch from RC5 to RC6

- Forgotten to change $var to $vars in line 380 of class.mailfetch.php
- Removed unneeded comment

Added php_gettext as primary translation engine

- Added php_gettext support (thanks to Danilo Segan and Steven
Armstrong)
- php_gettext is now the primary translation engine
- Extended language detection functionality

Add error/misconfiguration checks and fix undefined variables

The user should not have to step over it

Remove inline onClick/Submit events

* Change table name from ost_email_filter* to ost_filter*
* Add patch for target field.

Map each of the inputs from $_POST['ids'] into a separate, sanitized
database input (via the db_input() function), then implode() the array with
commas and build the SQL statement.

And correct several undefined function errors from several source files. So
while function names in PHP are considered case-insensitive, it still makes
sense to use consistent camel casing for both defining and calling methods.
The lint test searches the code base for method calls, and then searches the
code base again looking for a function definition matching the name of the
function invoked. It's not failsafe, because it doesn't detect the class
from which the method should belong, so it's likely to have false negatives.
Furthermore, it won't work well for PHP 5 where several classes are built
into PHP (and aren't searchable in the osTicket code base).

Remove the include/staff/api.inc.php as it no longer appears to be used (and
contains references to undefined methods).