Go to fullscreen in QWindoStateChangeEvent.

It is now possible to go properly to fullscreen also from Window
Manager's actions/shortcuts.
Added possibility to select text on page with Shift+Arrow keys.

Shift+Right Arrow        => select next char
Shift+Left Arrow         => select previous char
Shift+Ctrl+Right Arrow   => select next word
Shift+Ctrl+Left Arrow    => select previous word
Shift+Home               => select start of line
Shift+End                => select end of line
Shift+Ctrl+Home          => select start of document
Shift+Ctrl+End           => select end of document