Rename 'Standard Gaming Platform' to 'sgp' (#246)

* rename 'Standard Gaming Platform' to 'sgp'

* Adapt CMakeLists.txt files to renamed SGP directory

* Lowercase it

sgp/TopicIDs.h

@@ -0,0 +1,32 @@
+#ifndef _TOPICIDS_H
+#define _TOPICIDS_H
+
+const unsigned INVALID_TOPIC = 0xffff;
+
+const unsigned TOPIC_DECISIONS = 25;
+const unsigned TOPIC_MEMORY_MANAGER = 24;
+const unsigned TOPIC_FILE_MANAGER = 23;
+const unsigned TOPIC_DATABASE_MANAGER = 22;
+const unsigned TOPIC_GAME = 21;
+const unsigned TOPIC_SGP = 20;
+const unsigned TOPIC_VIDEO = 19;
+const unsigned TOPIC_INPUT = 18;
+const unsigned TOPIC_STACK_CONTAINERS = 17;
+const unsigned TOPIC_LIST_CONTAINERS = 16;
+const unsigned TOPIC_QUEUE_CONTAINERS = 15;
+const unsigned TOPIC_PRILIST_CONTAINERS = 14;
+const unsigned TOPIC_HIMAGE = 13;
+const unsigned TOPIC_ORDLIST_CONTAINERS = 12;
+const unsigned TOPIC_3DENGINE = 11;
+const unsigned TOPIC_VIDEOOBJECT = 10;
+const unsigned TOPIC_FONT_HANDLER = 9;
+const unsigned TOPIC_VIDEOSURFACE = 8;
+const unsigned TOPIC_MOUSE_SYSTEM = 7;
+const unsigned TOPIC_BUTTON_HANDLER = 6;
+const unsigned TOPIC_JA2INTERRUPT = 4;
+const unsigned TOPIC_JA2 = 3;
+const unsigned TOPIC_BLIT_QUEUE = INVALID_TOPIC;
+const unsigned TOPIC_JA2OPPLIST = 2;
+const unsigned TOPIC_JA2AI = 1;
+
+#endif	// NUM_TOPICS_IDS