added different multiplications and some possibilities for their syntax

* addition of a "rawten" type, also parameterized by \rho, which represents the type of tensors as they are stored in an image on disk or in memory.  As it was, images were only of type \rho, with no indication of the tensor structure.  The only annoyance now is that this allows one to store on disk or in memory tensors with int coefficients, which is probably nonsense, but its harmless.

* renamed the mapping of image to field from "sample" to "convolve".  However, its not clear to me if the definition as I wrote it is sufficiently clear that the mapping is from an image of rawten<o,d,\rho> to an field of tensor<o,d>, where the "o"s and "d"s must match up.

* added negation of fields

* moved what was in "tensor arithmatic" to the "addition" section.

fixing typos

  Added tensor+/-field operations

  Fixes.

  Preliminary design document

move math into doc

  Minor edit

  Working on type and operator design-space summary

  new file

  Initial commits