Enable sieve metermaid MTA option

Sieve language extension MTA options: (0-2)
New in the 8.0 release. The  MTA option controls whether Sieve filters may use the    operator to access and manipulate data stored in  MeterMaid. A value of 0 disables the use of the  operator in all Sieve scripts. The default value is 1, meaning that  may be used in any Sieve script. A value of 2 allows  to be used in system-level  Sieves only.

When  is set to , then  any attempt to use   will result in a Sieve error  "MeterMaid access has been disabled".

When  is set to ,  then user-level attempts to use   will result in a Sieve error  "MeterMaid only allowed in system-level sieves".

See also:
 * MeterMaid
 * Sieve metermaid extension
 * MeterMaid MTA options
 * Sieve language extension MTA options