Add algorithm usage examples

[NickDraper]

Cloned from http://trac.mantidproject.org/mantid/ticket/9614:

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Cloned from http://trac.mantidproject.org/mantid/ticket/9580:

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A dd testable algorithm usage examples.

There is help on how to document the algorithms in the following links:
http://www.mantidproject.org/Algorithm_Usage_Examples
And there are examples implemented for '''Fit, Load, LoadISISNexus''' and '''Rebin'''.

To create workspaces to use in your usages you should try to create the workspace using CreateSampleWorkspace or CreateWorkspace, and only use a file if you really have no other option and the size is small.

In Visual studio you have two targets to create the documentation and run the doc tests (docs-html and docs-test in a documentation subfolder). You will need to update your Third Party Library.

If you are using Linux/Mac look here: https://github.com/mantidproject/mantid/blob/master/Code/Mantid/docs/README.md

1. FakeMDEventData.cpp
2. IndexSXPeaks.cpp
3. GenerateEventsFilter.cpp
4. GetEi.cpp
5. Transpose.cpp
6. SpatialGrouping.cpp
7. FindDetectorsPar.cpp
8. LoadCalFile.cpp
9. LoadDspacemap.cpp
10. LoadNexusLogs.cpp
11. SaveDaveGrp.cpp

[NickDraper]

This issue was originally trac ticket 9615