Android client: folder filtering, and download support

[prefect47]

Two things:

1) The ability to select a folder and only show those files. Right now all folders are mixed, which is annoying since you usually want to either listen to music or view videos.

2) Downloading (transcoded or original) files through the client. This is more for video. If download was possible you could then use player apps on the Android device for playback instead of having to go via flash in the browser.

[ace518]

scroll to the top of the list of artists(folders) and click on select folder. You can then pick all, or individual folders you have setup on the server.