add a build_standalone cmake variable to install Qt files only if necessary. True by default on all platforms except Unix (because for all these platforms we provide standalone packages and for unix, we can do make install and this should not install Qt files).
add android activation system
Merge branch 'android buy'
gletters, limit the number of falling items to 3

It is too confusing to have too many items shown.
typographical quotes rather than straight quotes
add ukrainian language in the list, remove translation of languages and put country names in their language
translation of countries using the .po already filled
Improve font-sizes for tablet devices

On mobile devices with bigger screens some Text elements appeared too
small.
main: add dpi information to debugging output
dialog about, add the ratio to the images
color, based on educational feedback removed the voice on error

Children cannot remember the question if we provide the wrong answer
as audio.
Revert "Improve font-sizes for tablet devices"

This reverts commit 0594711942fcc56d73c5e71a842c36b133e99cbd.

Does not work well on hdpi devices like nexus 5, where fonts become
huge.
findit, put the repeat button out of the bar

When the bar is hidden the repeat button is missing.
menu, minor move of the fav icon on the left
code, no more compile the activation code unless requested

Add the WITH_ACTIVATION_CODE option in the cmake which is OFF
by default.
code, no more compile the activation code unless requested

complete previous commit.
core, added simplified chinese in the language selector
help dialog, better size of the icon

normalized icon size to suit the help dialog as html does not rescale well.
ballcatch, minor replace main by background

referencing main creates undefines when we change activity.
clockgame, add a drop shadow behind the question

trying to make the text easier to read.