add Player.IsInternetStream Infolabel

This adds a bool "Player.IsInternetStream" which might be used by addons and/or skins to determine if the currently playing file js a network stream by utilizing URIUtils::IsInternetStream (which in turn seems to be used at many places in the core code to accomplish the same).

A practical use case (and "emulation" in python) might be seen at https://github.com/herrnst/script.xbmc.lcdproc/blob/master/resources/lib/infolabels.py#L150 in InfoLabels_IsInternetStream(), which is used to determine if any webcast/stream/cloud icon on displays is to be lit (at https://github.com/herrnst/script.xbmc.lcdproc/blob/master/resources/lib/lcdbase.py#L519 ).

While implementing the check in python works fine, it might be a nicetohave thing for other addons and authors and any changes regarding added network URI protocols in XBMC's core will immediately be available in addons.