Adding scheduler component as requested in AGPUSH-673

Please test w/ EAP (6.3.beta), instead of JBoss AS 7.1.1

The main reason is, as listed in [AGPUSH-673](https://issues.jboss.org/browse/AGPUSH-673), a bug in JBoss' AS 7.1.1 EJB component.
s/maxium/maximum/

also:

possible rephrase "that's what we currently use as the maximum days the message information objects are persisted before wiped out automatically by the <link>DeleteOldPushMessageInformationScheduler</link>"