blueprint for nd iteration

[cyrush]

for better compatibility with Sidre N-D Fortran array support and python ndarrays

start with the contiguous case:

+shape (list of ints)
+values (actually 1-d array with values)

[cyrush]

this is evolving into a more abstract ND Iterator or ND Relation capability that will support:

values

along with:

shape
offsets
strides

strides and implicit shape have been explored in the context of structured meshes.

we are working on extensions to the mesh blueprint that will also demo offsets.