layers: Rename Layer/library/json files for consistency

Renamed layers from (for example) xxx_DrawState to xxx_draw_state
Renamed JSON files
Renamed libraries
Renamed object_track.* to object_tracker.*
Renamed apidump.h to api_dump.h
Renamed screen_shot layer to screenshot
Renamed APIDump layer settings file options to ApiDump
Bug fixes here and there from prior renames
diff --git a/layers/mem_tracker.cpp b/layers/mem_tracker.cpp
index d3e9a92..e2ac794 100644
--- a/layers/mem_tracker.cpp
+++ b/layers/mem_tracker.cpp
@@ -1240,7 +1240,7 @@
         "VK_LAYER_LUNARG_mem_tracker",
         VK_API_VERSION,
         VK_MAKE_VERSION(0, 1, 0),
-        "Validation layer: MemTracker",
+        "Validation layer: mem_tracker",
     }
 };