Add HDF5IO tests for add_read PR

[oruebel]

This PR targets #85 to complete open ToDo items to add unit tests.

Add unit tests for public HDF5IO-specific functions (i.e., not inherited from BaseIO)

• HDF5IO::getH5ObjectType
• HDF5IO::getNativeType
• HDF5IO::getH5Type

Add unit tests for new publicHDF5IO functions (which are core functions new inBaseIO). While some of these are partially covered by the DEFINE_FIELDS read tests, it will be useful to more fully test these separately

• HDF5IO::findTypes (implemented inBaseIO::findTypes)
• HDF5IO::readDataset (incl. with start, count, stride, and block parameters set). This is to test that reading subsets of larger arrays works as expected.
• HDF5IO::open(FileMode mode) test that file modes are being set correctly
• HDF5IO::readAttribute
• HDF5IO::getStorageObjectType
• HDF5IO::getGroupObjects
• HDF5IO::attributeExists
• HDF5IO::objectExists