[builder] Force Morsy radius to 1cm

It avoids some erratic behaviour of Morsy, at simulation startup, and
avoid it floats 1m above the ground
[core] Workaround against null rotation for dynamic objects
[actuator] Rework a bit the keyboard actuator

Make sure it is always called, and set a null speed if no key are
pressed. Otherwise, the robot continues to move until a new key is
pressed (modulo friction handling by the game engine).
[template] Replace use of deprecated camera positioning methods
[template] Set keyboard control type back to 'Position'

In this way, it 'works' as previously, but it is still an UB for my
point of view :).