Added further key bindings to slider

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
[cleanup] "constified" canvas drawing color

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
[cleanup] removed pointless NOP skin wrapper functions

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
[cleanup] moved multi-line text rendering to skin

More skinning related than canvas related. Also avoids having the same
parser copied accross multiple source files.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
Added missing memberof tags to skin functions

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>