core menu, added display of difficulty level.
core, added support for activity list sorting

2 sorts are implemented, by difficulty and by name. The
former is the default.
findit, minor code cleanup.
leftright, added support for left/right keys

Now we can play the activity with the left and right key
of the keyboard.
leftright, improved by grouping items

Now all the qml items are grouped in an Item that is
passed to the javascript. This avoid passing each graphical
item individually in the start.
leftright, added copyright headers
template, improved start with a grouped items

Added missing copyright headers.
core, minor, added copyright headers.
Merge remote-tracking branch 'upstream/master'