bug fix for issue 1739, two changes included:

* fix typo in OC_Group_Database::DisplayNamesInGroup's SQL clause
* check array_diff return value in OC_Group::displayNamesInGroups,
  when there is no difference between two arrays, it will return
  NULL, so we have to take care of it.
WebDAV-Testing:
- write the exception to the log
- in case curl is missing we should return true as well
[tx-robot] updated from transifex
Merge pull request #1768 from houqp/issue_1739

bug fix for issue 1739
add a safe_mode check
Merge pull request #1812 from owncloud/add-logging-to-webdav-test-master

Enhancment to the WebDAV-Testing ...
make number-input fields look like they should
rename app to 'deleted files'
Merge pull request #1830 from owncloud/fix_css_number

make number-input fields look like they should
fix giant advanced caret in installation
Update hint by the internal version number.

So we don't repeat the 4.5 <=> 4.90 mixup
Merge pull request #1836 from owncloud/update-version-remark

Update hint by the internal version number.
Merge pull request #1835 from owncloud/normalize-giant-caret

fix giant advanced caret in installation
Style cleanup files_sharing
Style cleanup files_trashbin
Style cleanup files_versions
Style cleanup core dir
Style cleanup settings
Join split translated strings
[tx-robot] updated from transifex