obmc-phosphor-image: devtools refactoring

Move i2c tools to the devtools package, right next to gpio tools.

Rename extrasdevtools to just devtools.  "Extra" doesn't convey any
useful information.  We can get away with this rename since noone is
touching the package.

Add an IMAGE_FEATURE for devtools, for easy opt-out.

(From meta-phosphor rev: 113fe568c65247e4dc99513b679b74c049178d36)

Change-Id: I28e8e6444e7d5d8c5c6b7c0fb6666587027b3a7b
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-phosphor/recipes-phosphor/images/obmc-phosphor-image.bb b/meta-phosphor/recipes-phosphor/images/obmc-phosphor-image.bb
index a0c14ff..c12b188 100644
--- a/meta-phosphor/recipes-phosphor/images/obmc-phosphor-image.bb
+++ b/meta-phosphor/recipes-phosphor/images/obmc-phosphor-image.bb
@@ -8,6 +8,7 @@
         obmc-bmc-state-mgmt \
         obmc-chassis-mgmt \
         obmc-chassis-state-mgmt \
+        obmc-devtools \
         obmc-fan-control \
         obmc-fan-mgmt \
         obmc-flash-mgmt \