hdfview

Merge pull request #70 in HDFVIEW/hdfview from ~JHENDERSON/hdfview:feature/AttributeNatTable to hdfview-3

* commit '613c37cf038f63c3ef0d71390aca5c31558e7800':
  Fix WidgetDisposeException in HDFView.java main class
  Rudimentary DataProvider for Scalar Attributes
  Rudimentary DataProvider for Compound Attribute reading
  Update TreeItem icon after adding/removing an attribute
  Re-organize classes into module packages