bmc: provide disabled json support

Provide support such that a json configuration file can define a firmware
handler and its behavior.  This is not yet enabled.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: If21f4e97951b3bb91a8afc53bee493d8600a04b7
diff --git a/.gitignore b/.gitignore
index 2b70727..9cb1b4c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -49,6 +49,7 @@
 
 # Custom generated files
 *.target
+*.json
 
 # Output binaries
 burn_my_bmc