samples/display: Introduce the cfb_shell sample app
This adds the shell sample app for the Character Framebuffer testing.
cfb - Character Framebuffer shell commands
Options:
-h, --help :Show command help.
Subcommands:
init :[none]
get_device :[none]
get_param :<all, height, width, ppt, rows, cols>
get_fonts :[none]
set_font :<idx>
invert :[none]
print :<col: pos> <row: pos> <text>
scroll :<dir: (vertical|horizontal)> <col: pos> <row: pos> <text>
clear :[none]
Signed-off-by: Diego Sueiro <diego.sueiro@gmail.com>