API: Add presentation state (default slice orientation)

[forderud]

Enable integrators to query the loaders for the default slice orientations when viewing image slices.

API: Limited "presentation state" support (GE proposal): #141

[ravimanaguli]

TestViewer and DummyLoader are essential for detail investigation and proper interoperability of loader DLL.

[1]
Please define range of PresentationState::GetViewCount() output. Max. value? Min. value?

[2]
What does Image3dSoruce::GetPresentationState() do?
It is [optional], is it not necessary to implement it?"

[forderud]

TestViewer and DummyLoader are essential for detail investigation and proper interoperability of loader DLL.

Fully agree. I will personally ensure that these projects are updated after we agree on the spec.

[1] Please define range of PresentationState::GetViewCount() output. Max. value? Min. value?

I would prefer to leave that to the implementers to decide, since it will likely be difficult to agree on specific values. For GE Vivid data, we'll likely return somewhere between 1 and 12 views, depending on how the files were originally stored. PACS integrators are free to only utilize the first "N" views when loading 3rd party data, and the GE EchoPAC integration will likely only utilize the first 3-4 views returned.

[2] What does Image3dSoruce::GetPresentationState() do?
It is [optional], is it not necessary to implement it?"

Correct. A conforming implementation can e.g. return E_NOTIMPL if it doesn't support presentation state (yet). The number of views returned might also be zero if no "view" information is present in the file.