Compile fixes for windows build to add libxml2
Updated HDF5 writer plugin to read in xml layout from string or file
Do not provide a default name for an element.  Fixed bug when looking for default ndattribute group, ensure the method recursively checks all groups.
Ensure the root element does not return any path or name, it is no longer a real group.
Updated to ensure a root element is always created along with the first specified group.  This new root element does not map onto a real HDF5 group.
Cleaned up code.  Added comments for methods.  Ensure private member variables consistent.
Major rework of code, cleaned up old comments, removed old and duplicated code.  Cleaned up iterator names and removed private member variables that are no longer used.
Removed the root group.
Added comments and removed some whitespace from the file.
Removed ELLNODE for HDFAttributeNode structure.
Added feature for HDF5 writer plugin so you can load xml layout throught a filename or a waveform. To do it throught a waveform it must start with <?xml.
Example: <?xml version="1.0" encoding="utf-8"?><start_tag> ... </start_tag>
Forgot brackets for if statement that checks file stat
Merge branch 'hdf5_xml' of github.com:aglowacki/ADCore into hdf5_xml
Merge branch 'hdf5_xml' of github.com:ajgdls/ADCore into hdf5_xml
Tweaked the error handling

This is just a minor tweak to bring error handling of NDFileHDF5::writeOctet
more in line with the usual ::writeNNN functions. The important bit is to
catch and report any errors that may occur in the business logic - i.e. in
the call to verifyLayoutXMLFile()
Removed superfluous call to callParamCallbacks()

This is not necessary at this point as the calling functions (at several
different levels) will also do that for us.