new activities:
* calendar
* family
* family find relative
* memory case association
* memory case association with Tux
* submarine
misc:
* Add Tutorial item to be able to have activity introductions with both images and texts (some activities can be updated to use it)
* Add easy mode in letter in word with less words displayed
todo:
* finish family new graphics
* find the date
* electricity
* add changelog in the code
* check if minimazing the code before release is useful ("find -type f -name \*qml -exec qmlmin {} ;" minus ActivityInfo.qml), seems to win 300ko for the apk, worth it?