EQL5-Android: Qt 5.7/ministro, sokoban example

[polos]

I switched the included EQL5 binary libs from Qt 5.9 to 5.7 because of the "ministro" deployment for Qt (currently, neither Qt 5.8 nor 5.9 are supported by ministro).

(But of course you can also cross-compile the eql5 libs with whatever Qt version you want; instructions are included, see 'build-eql5/' in sources.)

I finally added a port of the sokoban example (with screen buttons) for tablets.
An APK for ARM (3.6 MB) can be found here: sokoban (see also screenshot in sources).

Paul