Add the concept of built-in lists

Generalize custom list interface in order to provide for facility to manage
system's built-in list like ticket statuses, priorities ...etc.
Add ticket status list

First implementation of built-in custom list
Adopt translation work from Thane de Loth
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
Add POT generation for the i18n CLI utility
Fix some consistency issues
Bootstrap translations for staff members
Add translations for new and moved strings
Add gettext implementation optimized for osTicket
Complete translations for new content
i18n: Translate Redactor for staff panel
i18n: Make Redactor translated for client panel

This requires a hidden setting for the system language or the language
selection of the client (also currently hidden).
i18n: Add localization to the jQuery datepicker
Translate 'staff' to 'agent'
Final translation will not ship with PO and MO files
lint: Fix several detect issues
i18n: Translate javascript phrases
i18n: First attempt at translation documentation
i18n: Complete language pack compilation for PO files
i18n: Fix several small issues with translations
Add multiselect support to choices widget