More options for history generation

[NickDraper]

This issue was originally TRAC 3863

It's become clear that we need to add some more options to history generation. At the moment we take a best guess of what is actually desired, but we need to cover.

1. History to the last load event
2. Full history excluding intermediate load/save event
3. Full History

Ensure these are available both in the algorithm and in the History window.

[NickDraper]

@NickDraper (2012-01-09T09:43:05):
Moved to iteration 33 at iteration 32 code freeze

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@NickDraper (2012-04-30T14:12:18):
Moved at end of release 2.1

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@NickDraper (2012-08-10T12:43:28):
Moved at the end of release 2.2

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@NickDraper (2012-10-28T11:38:41):
Moved to milestone 2.4

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@NickDraper (2013-01-28T09:22:56):
Moved at the code freeze for release 2.4

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@NickDraper (2013-04-29T09:49:34):
Moved to r2.6 at the end of r2.5

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@NickDraper (2013-07-26T13:54:58):
Moved to backlog at the code freeze for R2.6

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@NickDraper (2014-02-14T11:04:55):
Bulk move to assigned at the introduction of the triage step

[NickDraper]

superceded by unrolling history