Pass _data->header to writeMagicNumberandVersionField()

Making this change in the OStream version of the constructor so that it
matches the const char * version. Otherwise we get a bug where files
made with an OStream won't get their version flags set properly.
A quick fix for dealing with deep data in exrdisplay.
This introduces a -noDeepComp / -d flag that simply presents the first sample in the samples list.
We also do a manual implementation of the deep comp for the tiled deep images.
@TODO implement the deep comp for the DeepTiled code.
Added a namespace alias file to make the code less verbose.
Merge branch 'item72' into develop