meta-facebook: obmc_functions : Add Command script

1. Add Command script to avoid shellcheck fail.
example.
gpioset $(gpiofind line_name)=1
need change to gpioset "$(gpiofind line_name)"=1 to avoid shellcheck
fail but it can't work.

2. Add set_gpio and get_gpio script for all meta-facebook platform

Usage:
set_gpio LINE_NAME SetValue

val="$(get_gpio "LINE_NAME")"

Change-Id: I99cb2e60e29a24a273d0bb9e0cb276106d730b22
Signed-off-by: Peter Yin <peter.yin@quantatw.com>
diff --git a/meta-facebook/recipes-fb/packagegroups/packagegroup-fb-apps.bb b/meta-facebook/recipes-fb/packagegroups/packagegroup-fb-apps.bb
index dd6eeab..e92b52d 100644
--- a/meta-facebook/recipes-fb/packagegroups/packagegroup-fb-apps.bb
+++ b/meta-facebook/recipes-fb/packagegroups/packagegroup-fb-apps.bb
@@ -64,5 +64,6 @@
         phosphor-fan-sensor-monitor \
         phosphor-gpio-monitor-monitor \
         tzdata-core \
+        fb-common-functions \
         ${RDEPENDS_PN_SYSTEM_EXTRAS} \
         "