Minor changes to the Official Library Spec

[Philippe Hurbain]

Clarification to Sticker Geometry:
- For stickers printed on a transparent medium, the type 1,3, or 4 lines that comprise the pattern shall be preceded by a 0 BFC NOCLIP statement and ended by a 0 BFC CLIP statement
- The pattern should be oriented such that the top of the pattern aligns with the +Z axis. Exceptions to this rule may be made on a case by case based.

Sorry to chime in late, but there is another point that could be clarified in BFC NOCLIP usage (for stickers or transparent parts): should color 16 (transparent section) of pattern be included in NOCLIP section or not? Case in point: https://www.ldraw.org/cgi-bin/ptdetail.c...973p08.dat
I initially thought that these transparent areas belonged to the pattern so should be placed in NOCLIP section, but this would cause inconsistencies with parts only partially patternable where most geometry is in a BFCed subpart, including areas next to patternable areas. So I now think that transparent surfaces should NOT be in NOCLIP section.