add license to keyboardlayout configGeneral.qml

So I did a quick glance through the file history and I can say I would prefer to keep only 2 persons in the list for now:
me (as an author) and @ngraham, as he did quite a big change adding "label+flag" display style option: !1131 (merged).

@saurov and @epopov did some important fixes/additions, so we could list them too if they wish.

All the work is respectful, it's just to keep the header small and manageable enough.
Hope it's fair.

cc @ratijas as he found the missing header and did some refactoring