Changed default number of threads and added auto value.

Changed default number of threads to 1 instead of autoconfigured value and
added a new `auto` variable which enables autoconfiguration of thread count.

The number of threads used when autoconfiguratio fails was changed from 4 to 1.

The default value of using N threads where N is the number of CPU cores was
not optimal as the possibility of rescheduling was higher the more utility
threads there were. Due to this, N-1 is deemed to be the better autoconfigured
value for thread count.

server/maxscale_template.cnf

@@ -3,12 +3,11 @@
 
 # Global parameters
 #
-# Number of threads is autodetected, uncomment for manual configuration
 # Complete list of configuration options:
 # https://github.com/mariadb-corporation/MaxScale/blob/master/Documentation/Getting-Started/Configuration-Guide.md
 
 [maxscale]
-#threads=8
+threads=1
 
 # Server definitions
 #