Fix errors when loading music album art.

Use RemoteFile::exists() instead of FindFile, it's more appropriate
here and faster.

StorageGroup expects a hostname not an IP address, pass the hostname instead.
Fix FindFile/FindFileLists using SendRecieveStringList() when accessed on Master Backend
More accurate error message when an IP is passed to GetBackendServerIP() instead of a hostname
Fix more IP vs hostname confusion in myth:// urls

A myth url consists of <group>@<hostname>:<port> where <hostname> is
the unique identifier of a backend, NOT an IP address. Some code
rightly expects to be able to extract the hostname from the URL and
use it as the unique identifier, for example to StorageGroup() or as a
key for DB lookups. The places where an IP was used broke this
assumption and caused the code to take an extended route to complete
it's task, or caused failures.

The 'hostname' will be converted to an IP address only at the point
where we connect to the remote backend to transfer/delete/etc the
file. Since only mythtv is expected to handle myth:// urls this is OK.

Since this has been causing confusion for some time there may be parts
of the code that incorrectly expect an IP address which will have to
be fixed.
Revert "HDHomeRun: Fix compilation on fedora 20"

This reverts commit 6c75467ac8d6f32874fd703b8e10b7d1127cade0.

Not needed as correct fix is in configure
Fix configure after the ffmpeg merge.
Resolves f20-qt5 compilation
UPnP: Add support for GetFeatureList() and GetServiceResetToken().

We don't yet support any features so we return an empty result.

For the ResetToken I used the date at the point the MediaServer was
started as it fits the critera of being unique (never repeating) and
it will change when the backend restarts (internal state is lost).
UPnP: Implement the CONTAINER_SHORTCUT feature.
Rework the way extensions register shortcuts without using a callback to the CDSObject
UPnP: Revert an unintended change which incorrectly encoded xml in response to GetFeatureList()
UPnP: Fix copy/paste error affecting ConnectionManager's GetFeatureList()