Updated code to use a common base class and single factory pattern.

Implementation of Operator classes using dynamic polymorphism.

assigned to @ccantwel

added 17 commits

• eedda94f - 1 commit from branch master
• 603d7cd5 - Initial design using inheritance
• 59c0b379 - Use enums for field state and operator type
• 5eeaa72b - Operator creation works with factory now
• d6212663 - Updated code to use a common base class and single factory pattern.
• 2e3f27fb - Fix brokenness with ErrorUtil.
• d147c562 - Tidy up. Put implementation in detail namespace.
• ab50ef5c - Memory region inheritence.
• ced187ef - Implement Field memory region backend infrastructure
• e03210e7 - Make output from main more clear
• 3ebfc930 - Automatically convert MemoryRegion in case of a failed cast
• 95c87476 - Fix bug where memory is not moved from device to host before converting
• 3cb0a677 - Add warning when requesting storage different from the current one
• bc5eb151 - Use ErrorUtil for Warnings
• d8fe5c25 - gitignore
• 97630747 - Add comments to Field, MemoryRegions and main
• 85e16749 - Add some more details to documentation.

Compare with previous version

mentioned in commit 9d211045

merged