Convert kcsbridged to C++17, sdbusplus::asio, and new IPMI D-Bus API

This rewrites the C-style kcsbridged in modern C++, taking advantage of
the sdbusplus::asio bindings. This also converts the bridge to use the
new IPMI D-Bus API, which is method based instead of signal/method
based.

Tested-by: Using a parameterized unit file, launching via
           sytemctl start phosphor-ipmi-kcs@ipmi-kcs3
    verify from host:
           modprobe ipmi_si
           ipmitool mc info

Change-Id: I3a3e85a23fa7b76814848fcf270d25e4510bdd77
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/phosphor-ipmi-kcs@.service b/phosphor-ipmi-kcs@.service
new file mode 100644
index 0000000..43cce3b
--- /dev/null
+++ b/phosphor-ipmi-kcs@.service
@@ -0,0 +1,13 @@
+[Unit]
+Description=Phosphor IPMI KCS DBus Bridge
+Requires=phosphor-ipmi-host
+After=phosphor-ipmi-host
+
+[Service]
+Restart=always
+ExecStart={bindir}/kcsbridged -c "%i"
+SyslogIdentifier=kcsbridged-%i
+
+[Install]
+WantedBy=multi-user.target
+RequiredBy=