ISSUE-37: the Graph and Links model

I've tried to make a short description of a model proposal which I believe covers composition/ aggregation, paging, creation and server directed application flow. For the moment it is called it the "Graph and Links" model :) I will try and fit an extended description onto the wiki. 

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The LDP-Rs at the service interface is a graph. This graph is an observable description of state. Interaction which changes the graph is the mechanism for advancing state forward. 

Each LDP-R is defined by its links. Out-going links can be grouped into collections (LDP-LC) according to their name. Each LDP-LC has a distinct address. It may be possible to append a new link to a LDP-LC using POST. The append request either result in creating a new resource before linking it, or linking to an already existing resource. This is directed by the server which makes discoverable the predicates which should be supplied as useful input. Finally, a LDP-LC representation can be split into pages. Then in order to shrink a representation of a LDP-R, this paging mechanism can be used to refer to subsequent pages of content. 

Roger