Allow OpCon to dynamically determine date/time formatting

Of our 142 global properties, 40 of them are various formats of $DATE, $SCHEDULE DATE, and $TIME. It would be great if OpCon could dynamically determine how to format a system date variable, based on some expression, without having to create a global property to accomplish this.

Some examples of how I envision this working today (11/02/2018), with only $DATE defined as a global property:

| Property Expression | Result |
| [[$DATE{mm/dd/yy}]] | 11/02/18 |
| [[$DATE{mm-dd-yy}]] | 11-02-18 |
| [[$DATE{mmddyy}]] | 110218 |
| [[$DATE{mm/dd/yy}(-1m)]] | 10/02/18 |
| [[$DATE{mm/15/yy}]] |

11/15/18

|

I think this would make OpCon much more flexible when it comes to using formatted dates based on a System variable. You wouldn't have to determine if the variable exists, create additional variables, or worry that you may be messing up another job by modifying a current variable format.