Vocabulary pages design overrides for UNECE publication

[kshychko]

@onthebreeze, we need to agree on the changes for vocabulary pages design before we get them published on unece.org.
My suggestion:

1. Using UNECE logo
2. Removing footer or replacing it with UN/CEFACT related links.

Jekyll allows to overried layout so it should be easy to maintain both edi3 and UNECE desings at the same repo.

[kshychko]

@webilhan, please use https://www.un.org/styleguide/ as the guidence.