Reorganize caching in TOD class about toast HOT 2 CLOSED

I now have a proof of principle code in a separate branch that implements aligned memory allocation in pure C. This is the start of the core C library that we need in any case for lots of things. I can use cython to create Numpy arrays from scratch with these memory buffers, and also disable the destruction of that memory when the numpy array is destroyed. These memory buffers are allocated outside of the python memory pool, so can be returned to the OS. Based on memory_profiler output, this technique seems to work. However, it does require care to ensure that all numpy arrays with references to that buffer are out of use before deallocation.

from toast.

This is fully implemented as of 3434030.

from toast.