Bug/grouped column reorder

Allow grouped headers to reflect any changes in column re-ordering.

Pivotal Story: 51573875 (Data Grid widget shows wrong header for data.)

Root cause analysis:
When drilled into a specific group, the header row is not part of the main content table, and so does not automatically reflect the changes in column ordering. We needed to add a callback to the 'jqGridRemapColumns' event which explicitly re-orders the grouped header columns.
Also, the code for displaying grouped headers needed to be modified to take into account the current column order and visibility (in 1pr_jquery.jqGrid.src.js)


__General Requirements__
- [x] Pull Request contains full description of changes
- [x] Link to the Pivotal Tracker story
- [x] Rebased against latest master branch
- [x] There are no `-1` code reviews (can only be overridden by Kyle)

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__Coding Standards__
- [x] Style guidelines are followed, code has been formatted
- [x] Code follows idiomatic language paradigms

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__Testing__
- [x] Test coverage has not decreased
- [x] There is no performance degradation
- [x] All appropriate automated tests are present
- [x] Appropriate seed data exists


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__Documentation__
- [x] Major design decisions have been documented on the wiki
- [x] Deployment impact (changes required for new services, configuration, etc.)
- [x] documentation links from Pull Request

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__UI/UX__
- [x] applicable (UI/UX has been changed)
- [x] reviewed for usability and design

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__Defect__
- [x] Feature or defect resolution has been manually tested and meets all requirements of the underlying story
- [x] Seed data sufficient to satisfy testing resolution of defect
- [x] Root cause analysis provided