Implement a Reverse activity

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Project Description

There are several situations where it would be useful to reverse the order of a dataset. This could be done more efficiently than a sort.  The change would need to cover the following particular cases:

• inline datasets. (These could generally iterate in reverse, imposing no run time overhead)
• grouped datasets - reverse just within the group
• local
• global.

There is also opportunity for various optimizations - e.g., REVERSE(SORT())->SORT'

More details coming soon.

If you are interested in this project, please contact Gavin Halliday.

Completion of this project involves:

• Adding the syntax to the language
• Adding support for a new logical operation
• Generate the activity helper
• Add support for grouped and local reverse to all the engines
• Add support for global reverse to Thor.
• Implementing REVERSE for an inline dataset operation
• Investigate what optimizations can be performed

By the mid term review we would expect you to have:

• Add syntax, and represent a new logical operation 
• Produce test cases for the different variants
• A grouped and local variation of the activity implemented in one of the engines.