Support for HDF i/o and metadata

[jcrivenaes]

• Support HDF format for all public classes, both for files and memory streams as prototype
• HDF finalize, post prototyping
• Automatic detection of formats wrt to which object the file belongs to
• Support for custom and flexible MetaData in xtgeo is closely linked to this
• Metadata (as a seperate YAML file) shall be supported for other files also, in priority of irap binary surface

This work is closely related to SUMO, cf. @perolavsvendsen

[jcrivenaes]

See also #353