[QB] ISSUE-34 proposed resolution

As it says in the ISSUE description ...

"""
The Data Cube slice mechanism allows hierarchical organization of slices 
though the use of qb:subSlice.

However, it is not possible to distinguish between different levels of 
sub-slice when defining attachment levels, which in terms makes 
abbreviated formats for such cubes under-defined.
"""

While it would be possible to fix the issues the subslice mechanism is 
not part of SDMX and I've not seen its use in "in the wild" Data Cubes, 
perhaps because of the lack of clarity.

Proposal: remove qb:subSlice (leaving it in the ontology but marked as 
deprecated and removing mention of it from specification document).

Dave