RESQML to resqpy attribute name mapping

[andy-beer]

In general resqpy does not use the same names as RESQML either for high level object classes, nor their attributes. One of the tutorials already shows the mapping between class names. This issue is to add more detailed information on the mapping of attribute names.

[andy-beer]

As a first step towards this mapping, the RESQML attributes for each obj_* class have been listed in a new tutorial page.