It was only used on OS X and couldn't be used by the FinderSync
extension since that one runs in a sandbox. So use the same system
to load images in the legacy extension by shipping them in the
extension bundle instead of the owncloud.app bundle.
This is also given that the legacy extension needs padded icons
while the FinderSync one needs unpadded icons.
This prepares the switch to the official FinderSync API on Yosemite
which requires the extension to run in a sandbox. This complicates
the usage of a local socket to communicate with a non-sandboxed GUI
client. An NSConnection is easier to use in this case, which we can
use as long as the server name (i.e. Mach port registered name) is
prefixed with the code signing Team Identifier.
A placeholder server implementation is also added to the client's
SocketApi which basically reproduces the interface of a QLocalSocket.
Most of the references to individual sockets we're only using
QIODevice methods so the type was simply reduced. A typedef to
replace the QLocalServer was the only other part needed.
