config: move kernel configuration to independent file

Move to kernel/Kconfig

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
introduce initialization hooks

Close #30
config: centralize development configuration

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
kernel: get rid of redundant prefix f9 in init-hook
config: move options to config system

Move DEBUG, CONFIG_DEBUG, CONFIG_KDB to kernel/Kconfig

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
kernel: unify the consistent naming, init_hook
Merge remote-tracking branch 'vh21/tweak-dbg'
mk: minor comment update