Move template code from lib/Data to template file

Fix #1729
Change license header to small version and replace echo with p()

Fix #1729
Fix outdated setting layouts (admin & user page) and wrapping some strings
with t()

<fieldset> tags were not used in css files and this was causing settings
to be seen unaligned (enable admin_migration and see the admin page
for example).
changed all fieldsets into <div class='section'> instead.
Correctly check whether previewImageLink is set

Fix #1729
Do not use echo for html in template/list.php
Remove more HTML echo
Add missing callCheck() to ajax/settings.php in Activity App

As per https://github.com/owncloud/apps/issues/1705#issuecomment-39579951
minor tweaks with layouts
remove unmaintained/moved files_tree app
remove unmaintained/moved xmpp app
[tx-robot] updated from transifex
Merge pull request #1749 from owncloud/remove-unmaintained-files-tree

remove unmaintained/moved files_tree app
Merge pull request #1730 from owncloud/issue/1729

Move template code from lib/Data to template file
[tx-robot] updated from transifex
[tx-robot] updated from transifex
[tx-robot] updated from transifex
[tx-robot] updated from transifex
Merge pull request #1742 from owncloud/activitiy/add-call-check

Add missing callCheck() to ajax/settings.php in Activity App
[tx-robot] updated from transifex
adding support for plural forms