#97 Write basic "terms of reference" for EPICS V4

[Greg White]

Much of our documentation makes reference to entities and concepts that are not well defined or described. Adding definitions and making reference to those definitions in the documents, would much improve their readability. Eg,
define and provide references for "top level structure", "introspection
interface", "channel", "record" etc. Must much better distinguish references to
V3 items and disambiguate such terms, e.g. use of the term "channel access"
sometimes to refer to the generic control protocol, and sometimes to refer to
"Jeff Hill's" Channel Access. Make use of uppercase, quotes, italics
consistent.