Modified the Directed Graph nodes to have a Data payload
Modified the NamedNode to contain a variable payload
Added a Function Node and a Source node which form the two types of node in the graph

The orchestrated graph is now a graph of sources and in/out functions. Nothing more
NamedNode instances are now either streams or functions
Edited RIFConst and subclasses to implement a getDatatype method that returns the IRI of the datatype of the const.
Corrected many errors concerning the processing of RIF, including some flat out mistakes, and one miscomprehension of the Frame element (multiple slots are possible, necessitating the conversion of RIFTriples into RIFFrames, which can have multiple predicate-object pairs associated with one subject).
Merge branch 'master' of github.com:sinjax/squall