Further clean-up of src/keymap.cpp
Further clean-up of src/keymap.cpp

* OP_OPEN doesn't do anything in the help menu and in podbeuter, so it
  shouldn't be marked as being available there.
* Use KM_BOTH where appropriate.
* Make reload available in the articlelist.(Fixes #333)

newsboat/newsboat,der-lyse/newsboat,newsboat/newsboat,der-lyse/newsboat,der-lyse/newsboat,newsboat/newsboat,der-lyse/newsboat,x4121/newsbeuter,x4121/newsbeuter,der-lyse/newsboat,newsboat/newsboat,der-lyse/newsboat,newsboat/newsboat,newsboat/newsboat,newsboat/newsboat,x4121/newsbeuter,der-lyse/newsboat,newsboat/newsboat,der-lyse/newsboat,x4121/newsbeuter