first implementations for a new smartphone interface
deb: preview mode, different canvas aspect ratios
impl: #8 (mobile device interface)
deb: drawing on different device sizes
impl: #8 (mobile device interface) : sliding panels
impl: #8 (mobile device interface) : sliding panels / styling
impl: #8 (mobile device interface) : footer / styling
impl: #8 (mobile device interface) : controls / styling