Returns and update tags through WebDAV PROPFIND and PROPPATCH

Added oc:tags and oc:favorites in PROPFIND response.
It is possible to update them with PROPPATCH.
These properties are optional which means they need to be requested
explicitly
Return UID instead of login name

Without this OCS on LDAP is broken for API requests coming via Basic Authentication...
Add ultra-slim hack for incognito mode

As discussed at https://github.com/owncloud/core/pull/12912#issuecomment-67391155
Update 3rdparty submodule to restore PEAR5.php
Only populate tags in main file list

Moved populateTags to be done on the main file list.
This prevents the public file list to go through the same code and cause
an error when there is no user.
Remove obsolete method
Fix code style issues for tags plugin
change 'update' to more understandable 'change', fix #10408
change 'Allow Public Upload' to more understandable 'Allow editing', fix #10438
Mail address of users is now changable in the user management

* introduced new route settings/users/{id}/mailAddress
* kept old responses
* better error messages
* dropped lostpassword.php from settings/ajax
* cleaned up the UserList.add() and hand in user object instead of
  each attribute as another parameter
* check for change permission of mail address
* proper response messages
fix feedback for app navigation when using keyboard
fix feedback for apps menu when using keyboard
first part of fixing feedback for file list when using keyboard
introduce first 'Skip to content' button
improve keyboard navigation feedback for certain buttons
proper feedback for breadcrumbs when tabbing with keyboard
HHVM: In APC cache clear, only request the cache key in APCIterator.

The default value of the $format parameter of the APCIterator constructur is
APC_ITER_ALL which instructs the iterator to provide all available information
on cache values being iterated over. Only the key value is necessary for
matching and deletion via apc_delete(), though.

This prevents a "Format values FILENAME, DEVICE, INODE, MD5, NUM_HITS, MTIME,
CTIME, DTIME, ATIME, REFCOUNT not supported yet." notice on HHVM.
[tx-robot] updated from transifex
Merge pull request #12865 from owncloud/files-tags-webdav

Returns tags through WebDAV
Merge pull request #12948 from owncloud/wording

Wording fixes for sharing dialog