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.

server/modules/routing/avro/avro_schema.c

@@ -19,16 +19,16 @@
 #endif
 
 #include <avrorouter.h>
-#include <mysql_utils.h>
+#include <maxscale/mysql_utils.h>
 #include <jansson.h>
 #include <stdio.h>
 #include <limits.h>
 #include <unistd.h>
-#include <log_manager.h>
+#include <maxscale/log_manager.h>
 #include <sys/stat.h>
 #include <errno.h>
-#include <skygw_utils.h>
-#include <skygw_debug.h>
+#include <maxscale/skygw_utils.h>
+#include <maxscale/skygw_debug.h>
 #include <string.h>
 #include <strings.h>
 #include <maxscale/alloc.h>