Change the copyright of the license

[topiasv]

Currently the license has a copyright pointing to Free software foundation. It should be changed to @sleepsounds name or with his permission for this whole organisation. Should @sleepsounds allow it, I think the best thing would be to apply it for the whole group and list all contributors in a separate file as suggested in #9. This is of course first and foremost his decision and any other contributors hold the copyright for their own contributions unless stated otherwise.

[topiasv]

Example:

LICENSE file:
Copyright (C) 2018 sfos-ja group.

CONTRIBUTORS file:

Sleepsounds, name <email>
helicalgear, name <email>
knokmi612, name <email>
toxip, name <email>

[knokmki612]

license header of some src files also needs change.

https://github.com/sfos-ja/jolla-kbd-flick-jp/tree/master/src

Other than KeyboardBase_Flick.qml seem originally written by @sleepsounds