Document the design patterns for the temporal relationships

[cmungall]

We should have a .md page on the site documenting the DPs for TRs. These were all well-thought out based on definitions from @dosumis and Fabian Neuhaus, but you don't get the big picture from just exploring in Protege.

The page can describe the general approach, explain the use of the starts/ends functions in the textual definitions, and have some visuals showing the different relations, and some background on relationshipship to allen algebra

In

• Add symmetry and definition to simultaneous with #611

@dosumis notes we should have FOL theorem proving over these - which we definitely should. But the first step in just a bit more documentation