Should be able to specify TZ for SCHEDULED requests

[whitedr]

CronExpression in the Quartz library has the ability to set the TimeZone that the cron expression should be resolved in (see: http://www.quartz-scheduler.org/api/2.1.7/org/quartz/CronExpression.html#setTimeZone(java.util.TimeZone)). It would be nice if the SingularityRequest provided an optional string field called scheduledTimeZone that could be set to a valid TimeZone (i.e. passed to java.util.TimeZone.getTimeZone) and then have this field be used when building the CronExpression to test within SingularityScheduler.