Minor changes to the Official Library Spec

[Chris Dee]

Based on feedback, I'd like to proposed a few minor changes to the Official Library Spec:

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.

Claification to Sticker Shortcuts:
- Require a !KEYWORDS entry with text similar to Pattern !KEYWORDS Entry:
A sticker shortcut should, at a minimum include at least one !KEYWORDS entry in the form of Set <set number> where <set number> is the number of an official LEGO set in which that pattern appears. Only one set need be listed but more can be if desired.[/b]

I approve, with a minor change to the second proposal: "... in which that pattern appears." --> "... in which that sticker appears."