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

Use the admin-configured time format for formatting the values in the time
dropdown as opposed to always using 24-hour time.

Process inline attachments in thread entry and support inline images in
piped emails

Support inline images across the system, with draft support

Migrate to a single attachment table
    That way we don't need a new table for everything we need to attach an
    inline image to (like a signature, for instance)

Add richtext support for internal notes

Implement images on site pages

* Image paste in Redactor
* Make non-local images optional
* Placeholder for non-local images
* Fix local image download hover
* Don't re-attach inline images

Also, allow for the administrator to manually define the ROOT_PATH in the
config file (the very last mile).

If unable to detect the root path, provide a fallback ROOT_PATH setting to
'./'. This is likely to happen if run from the commandline (like for crons)
or if DOCUMENT_ROOT and the folder of main.inc.php seem to have nothing in
common

Fixes #704

Use mysql connection timing as the random seed, along with the microseconds
of the current time.

Change href definitions for embedded links in the ticket thread so that the
click will be bounced through a script. This will hide the original referrer
URL where the link originated.