Implement config parsing

Add a configuration json parsing function to read the configuration file
from /usr/share/binaryblob/config.json for which system file and location
to serialize/deserialize the binarystore blobs. Add a simple unit test for
parsing configs as well.

Signed-off-by: Kun Yi <kunyi731@gmail.com>
Change-Id: Ie86d622e83991365bc202d659f5860ff01190311
diff --git a/configure.ac b/configure.ac
index 2b09776..5ea68ed 100644
--- a/configure.ac
+++ b/configure.ac
@@ -24,6 +24,7 @@
 PKG_CHECK_MODULES([PHOSPHOR_LOGGING], [phosphor-logging],, [AC_MSG_ERROR([Could not find phosphor-logging...openbmc/phosphor-logging package required])])
 AC_CHECK_HEADER([blobs-ipmid], [AC_MSG_ERROR(["phosphor-ipmi-blobs required and not found."])])
 AC_CHECK_HEADER(boost/endian/arithmetic.hpp, [])
+AC_CHECK_HEADER(nlohmann/json.hpp, [])
 
 # Check/set gtest specific functions.
 PKG_CHECK_MODULES([GTEST], [gtest], [], [AC_MSG_NOTICE([gtest not found, tests will not build])])