Make gspo, graph and annotation terminology consistent

[fbaumgardt]

gspo stands for an {g:{ token:"", value:"" },s:{ token:"", value:"" },p:{ token:"", value:"" },o:{ token:"", value:"" }} SPARQL binding for quads. Currently it's sometimes used for a variant where the value is assigned directly to the g/s/p/o properties.

graph or body is the body of an oa:Annotation identified with the oa:hasBody relation. Currently it's being called graph, body or annotation, where annotation is supposed to have the meaning stated below and body is also used to refer to the HTML body of the entailing document.

annotation is supposed to be the full set of quads that make up an annotation, including the body and the metadata.

Moving to a consistent terminology throughout source code and documentation will improve readability.