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.

query_classifier/qc_dummy/qc_dummy.cc

@@ -11,8 +11,8 @@
  * Public License.
  */
 
-#include <modules.h>
-#include <query_classifier.h>
+#include <maxscale/modules.h>
+#include <maxscale/query_classifier.h>
 
 qc_parse_result_t qc_parse(GWBUF* querybuf)
 {