PEL: Read the compatible system names property

The chassis object in the inventory has (or rather at the time of this
writing: will have) a Names property that contains a list of the
compatible system types for the current system.  An example is:
["company-systemA-4G", "company-systemA", "company"].

Add this to the DataInterface class, and remove the previous
'getSystemType' API that was there but was still stubbed out.

Also change all the calls from getSystemType() to the new call
getSystemNames(), and check against all entries in that array to see if
the desired name applies to the current system.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I86aa0c15c564153fea612f407c161dfe9041fce6
diff --git a/extensions/openpower-pels/dbus_types.hpp b/extensions/openpower-pels/dbus_types.hpp
index 1a95c8b..8743f8f 100644
--- a/extensions/openpower-pels/dbus_types.hpp
+++ b/extensions/openpower-pels/dbus_types.hpp
@@ -9,7 +9,8 @@
 namespace openpower::pels
 {
 
-using DBusValue = std::variant<std::string, bool, std::vector<uint8_t>>;
+using DBusValue = std::variant<std::string, bool, std::vector<uint8_t>,
+                               std::vector<std::string>>;
 using DBusProperty = std::string;
 using DBusInterface = std::string;
 using DBusService = std::string;