Re-Spec references for LDP WG documents

Hi,

At the moment we have three references in biblio.json [1] with keys
LINKED-DATA-PLATFORM,
ldp, and ldp-ucr. Shall we

1. Unify LINKED-DATA-PLATFORM and ldp into one (using one as an alias)
2. Add references to the best practices guide, primer, and test cases
document

More concretely, following changes
https://github.com/nandana/specref/commit/aad378fc37fb932985c6bb08b501b4dedd897c3a

If that is ok, I can make a pull request to update biblio.json.

Best Regards,
Nandana

[1] - https://raw.github.com/tobie/specref/master/biblio.json