Metacat

Modifications to metacat rest service to use the new DataONE CrudService for
get() operation. Minor issue with permissions errors propagating up the
stack, but otherwise this is the first implementation of a full DataONE
method.

Modified readFromMetacat() to pass most exceptions up the call stack, which
allows creation of new entry points for calling reads. Still need to
continue factoring out the HTTPServletResponse that is passed in in order to
make entrypoints that are not servlet based possible. Problem now is in...