Handle Note Pixbuf

[pyluyten]

DONE : Note pixbuf from content ( bjb-controller.c)
DONE : Note pixbuf does retrieve Note color
DONE : Update pixbuf when note content changed
DONE : move pixbuf creation to libbiji
DONE : Note pixbuf looks quite uggly. Use shadow.
TODO : List view should have its own icon ( standard memo icon )