Hide concrete5 version number in upgrade page

If the constant APP_VERSION_DISPLAY_IN_HEADER is set to false,
unregistered visitors can still determine the currently installed
version by visiting the page /index.php/tools/required/upgrade.
Let's hide the version number when APP_VERSION_DISPLAY_IN_HEADER is
set to false.
Allow users to search for localized group

Groups are listed by their localized names. So, let's enable users to
perform searches by localized names...
Avoid translation misunderstanding for 'Set Number'

'Set number' could mean "Set the number" and "Number of the set".
Let's add a translation context to declare that in this case it means the
latter.
Switch to en_US when running the upgrade script

Since we store strings in en_US and translate them in the view side, let's
ensure that the upgrade process runs in en_US.
Emable support for en_US custom group names
Fix setup when language is not en_US
Fix error not showing error message on block type refresh error.
use 16:9, it's what youtube uses too
fix rowspan for user column
Merge pull request #1803 from Remo/form-export-rowspan

fix rowspan for user column
use default values from youtube.com
Merge pull request #1802 from Remo/youtube-width-height

use 16:9 as default dimension in youtube block
avoid Zend_Date when not needed

closes #1800
Merge pull request #1780 from mlocati/fix-localized-setup

Fix setup when language is not en_US
Merge pull request #1764 from mlocati/avoid-translations-misunderstandings

Avoid translation misunderstanding for 'Set Number'
Merge pull request #1766 from mlocati/upgrade-always-in-english

Switch to en_US when running the upgrade script
Merge pull request #1524 from mlocati/allow-searching-localized-groups

Allow users to search for localized group
Merge pull request #1794 from juhanihaapala/master

Fix error not showing error message on block type refresh error.
Fix error message on add attributes page
Merge pull request #1805 from hissy/fix-error-msg

Fix error message on add attributes page