Change the term Web Vocabulary to just vocabulary about json-ld.org

[msporny]

I started off using "Vocabulary" in the document and found it to not convey that we were talking about a special type of document. We should probably define what a Web Vocabulary is somewhere in the document. I'll do that now and refer to it when discussing "Web Vocabularies". We don't want people to get the impression that a "vocabulary" is just like a dictionary - ie. it's not machine-readable.

[msporny]

I added a term definition in the spec for "Web Vocabulary" and referred to that definition throughout the document. I will try to make usage of that terminology more consistent throughout the spec when I go through it again to clean up the prose.

[msporny]

Upon further thought, "Web Vocabulary" is strange... we want the document to be fairly accessible and I think defining and using the term "Web Vocabulary" takes us in the wrong direction. So, I implemented Markus' suggestion and changed every occurrence of "Web Vocabulary" to "vocabulary":

http://json-ld.org/spec/ED/json-ld-syntax/20120122/#dfn-vocabulary