[Blitz-support] Proper iterator support

[Neal B. <ndb...@gm...>]

I've been enjoying blitz++ - until now.  It seems the iterators are _very_ 
limited.  This pretty much kills generic programming (writing algorithms that 
will work with not only blitz, but also ublas, etc.).

I don't think it would be difficult to improve this.  Has anyone worked on it?

Here is a simple plan of attack:

* Use boost::iterator_adaptor to adapt T*
* Start with a simple, general implementation.  Array<T,N>::iterator just 
leverages operator(i,j,k).  Not efficient, but easy.
* Use partial specialization for Array<T,1>.  This is also easy.

Then, add specializations for higher dimensions if motivated.