[Kernel] Implemented Game Info Database

This aggregates XDBF and XLAST into one entity.

Replaced UserData::Key into more versatile AttributeKey for future usage in properties

src/xenia/kernel/util/xuserdata.h

@@ -16,6 +16,16 @@
 namespace xe {
 namespace kernel {
 
+union AttributeKey {
+  uint32_t value;
+  struct {
+    uint32_t id : 14;
+    uint32_t unk : 2;
+    uint32_t size : 12;
+    uint32_t type : 4;
+  };
+};
+
 enum class X_USER_DATA_TYPE : uint8_t {
   CONTENT = 0,
   INT32 = 1,