Solve some possible GSOD in ChannelSelection.py

Especially when no service is selected in empty bouquets or when some
context options are not available, while there exist a direct key to it
Bring back pip and play in mainscreen in context menu only when required

And also correctly block the direct "color" key
Merge branch 'master' of git://git.code.sf.net/p/openpli/enigma2 into BETA
Merge branch 'master' into BETA
Only show fixed columns when the service is playable

As it is only required when EPG is possible
Merge branch 'master' of git://git.code.sf.net/p/openpli/enigma2 into BETA
Update PluginBrowser.py