Readme updates

Cleanup and formatting and adding audio binary addons info to readme.linux

Both README.linux and README.ubuntu updated.

If there are any dependencies changing please let me know so I can update these docs accordingly at the same time.
Im only adding that cause 5024 if this isnt needed then never mind, ill revert back.

I will need proper instructions on prv addons compiling along with xbmc, since I never used them I dont really know anything at all about it.