Add exclusion for OSX ._<filename> files

Exclude older OSX metadata ._<filename> files from sync, improving
cross-platform sync experience.

Tested-on: arcturus <20 Nov 2013>
Merge pull request #1 from owncloud/master

Merge with owncloud:master
[tx-robot] updated from transifex
Remove misleading error message of "unknown error" for custom errnos.
Use a different key than "user" to store the shib user

There is a HACK from commit fa0a2764a40d5955f1d3426481f998a370223290
Which save the http user as a user for all credidentials, but that
cannot work with shibboleth

Fixes https://github.com/owncloud/enterprise/issues/175
Merge pull request #1179 from tomswartz07/master

Add exclusion for OSX ._<filename> files
WIP: CookieJar changes