OmeroCpp: Group code into folders

--no-rebase

The naming and organisation can be changed trivially if needed.

https://github.com/openmicroscopy/bioformats/pull/1322 does the Google Test grouping.

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Testing:

On Windows, run CMake with the appropriate Visual Studio generator.  Open the `openmicroscopy.sln` solution file.  In the "Solution Explorer", you should see the libraries, tests, examples etc. grouped as shown below.


![vs2012-omerocpp-group](https://cloud.githubusercontent.com/assets/1528953/4167103/5fdce71a-3510-11e4-892b-20359a639d09.png)