[Owncloud] Removing OC_Files

[Robin Appelman]

I'm currently in the process of removing code from OC_Files and putting it in 
a better place if needed.

I've been wanting to get rid of OC_Files for a long time, which is mostly a 
relic from the time before OC_Filesystem was around, the code in there is 
either a simple wrapper around the other filesystem classes 
(getdirectorycontent, move, rename, etc) or simple belongs somewhere else 
(download as zip, set upload limit) and it only adds confusion by having yet 
another filesystem related class.

While removing functions from OC_Files I'll try to adjust any code in master 
making use of that function, so nothing in master should break.

However, if you maintain a 3rd party app or some other code outside git master 
you should removing any dependency on OC_Files or it will break for tge next 
major version. If you're using something in OC_Files that does not a have a 
proper replacement yet, poke me on IRC or here on the ML about it.

 - Robin Appelman