check if settings.xml file exists or not

[mzfr]

Fixes #127

[razzeee]

This is not what we want. settings.xml is optional, not mandatory.

What martijn is aksing for in that ticket is, that if this file exists, we check for the format of the xml. As there is an old format and a recommended new one.

[MartijnKaijser]

Correct:
old format
https://github.com/xbmc/xbmc/blob/master/addons/metadata.themoviedb.org/resources/settings.xml
new format
https://github.com/xbmc/xbmc/blob/master/system/settings/settings.xml