Ordering of PEnum items

*Note that this is a minor issue that only affects documentation.*

At some point the decision was made to order PEnum items alphabetically with `notset` et al. last.

It was brought to our attention that manual ordering of penum items was explicitly implemented in IfcDoc.

At least in one case there is a meaningful discrepancy

PEnum_BackInletPatternType

Where the original was:

1/2/3/4/12/13 ...

One now we have (per character lexicographically)

1/12/123/2 ...

This can be solved by either:
* bring back the explicit ordering by means of the UML tags
* sort more intelligently (i.e Natural Ordering https://en.wikipedia.org/wiki/Natural_sort_order) to at least solve the particular issue where this was observed.