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.

client/maxadmin.c

@@ -48,7 +48,7 @@
 #include <getopt.h>
 #include <stdbool.h>
 
-#include <version.h>
+#include <maxscale/version.h>
 
 #ifdef HISTORY
 #include <histedit.h>