Move headers from server/include to include/maxscale

- Headers now to be included as <maxscale/xyz.h>
- First step, no cleanup of headers has been made. Only moving
  from one place to another + necessary modifications.

avro/maxavro_schema.c

@@ -14,8 +14,8 @@
 #include "maxavro.h"
 #include <jansson.h>
 #include <string.h>
-#include <skygw_debug.h>
-#include <log_manager.h>
+#include <maxscale/skygw_debug.h>
+#include <maxscale/log_manager.h>
 
 static const MAXAVRO_SCHEMA_FIELD types[MAXAVRO_TYPE_MAX] =
 {