change Pixelmed Attribute.read methods to support ReadStrategy

[irrer]

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Currently, the Pixelmed library does not have a way to stop the reading of a DICOM file based on application defined criteria. This program gets around this by reading in a small portion (first 4K) of file and interpreting what it can to get the metadata needed to categorize the file. This is done because it is much faster than reading the entire file, and greatly enhances the user experience when reading hundreds or thousands of files.

The proposed solution is to change the Pixelmed library to support a read strategy defined by the application. This would require acceptance by Pixelmed. It would get rid of exception messages thrown and ignored when reading DICOM files. These messages are distracting during development, as are noise that that can obscure noteworthy exceptions.