ipmid: Add command filter mechanism

Every ipmi command will pass through a filter prior to execution by the
registered handler. The filter consists of all registered filter
handlers that all must either return an IPMI error code or allow the
command to be executed. If any of the filter handlers return an error
code, the remaining handlers will not get a chance to run.

Each handler, executed in registered priority order, can be passed the
full message, or just the context (metadata describing the command,
netfn, cmd, etc.)

Change-Id: I3c48f19ebae0d24344b15fbcd2b940a32f8511d7
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/include/Makefile.am b/include/Makefile.am
index 4c0e899..852b26b 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -1,5 +1,6 @@
 nobase_include_HEADERS = \
 	ipmid/api.hpp \
+	ipmid/filter.hpp \
 	ipmid/handler.hpp \
 	ipmid/message.hpp \
 	ipmid/message/pack.hpp \