message: add more comments to conduit data coll
diff: namespace mfem
  {
  -/** @brief Data collection that uses the the Conduit Mesh Blueprint
  +/** @brief Data collection that uses the Conduit Mesh Blueprint
  specification. */
  /** ConduitDataCollection provides json, simple binary, and HDF5-based file
  - formats for visualization or restart.
  + formats for visualization or restart. It also provides methods that convert
  + between MFEM Meshes and GridFunctions and Conduit Mesh Blueprint
  + descriptions.
  For more information, see:
  - - LLNL conduit/blueprint library, https://github.com/LLNL/conduit
  + - LLNL conduit project, https://github.com/LLNL/conduit
  - HDF5 library, https://support.hdfgroup.org/HDF5
  @note The ConduitDataCollection only wraps the mfem objects to save them and
  @@ -41,19 +43,23 @@ namespace mfem
  Meshes and GridFunctions and Conduit Mesh Blueprint descriptions.
  Those that describe MFEM data using Conduit (MFEM to Conduit Blueprint) try
  - to zero-copy as much of data MFEM as possible. As a result the conduit node
  + to zero-copy as much of data MFEM as possible. The Conduit node result
  will not own all of the data, however you can easily make a copy of
  - resulting node when necessary.
  + the result node using Conduit's API when necessary.
  Those that construct MFEM objects from Conduit Nodes (Conduit Blueprint to
  MFEM) provide a zero-copy option. Zero-copy is only possible if the
  blueprint data matches the data types provided by the MFEM API, for example:
  ints for connectivity arrays, doubles for field value arrays, allocations
  that match MFEM's striding options, etc. If these constraints are not met,
  - MFEM objects that own the data are created and returned.
  + MFEM objects that own the data are created and returned. In either case
  + pointers to new MFEM object instances are returned, the zero-copy only
  + applies to data backing the MFEM object instances.
  @note QuadratureFunction%s (q-fields) are not supported.
  + @note AMR Meshes are not fully supported.
  +
  @warning This class is still _experimental_, meaning that in future
  releases, it may not be backward compatible, and the output files generated
  by the current version may become unreadable.
  