Fix crash

UnoKeyboardPS2::getLastEvent internally now uses
static variable to hold a reference returned from
function whereas class pointer is updated to NULL.
Configurations groups and keys values

Now fetched keys can be matched in narrow range of defined
values. Also, internally used configuration is aggregated inside
namespaces. Crucial pointers were marked with volatile keyword.
Unfortunately this is not perfect solution for untracked UNO
crashes.