Fixed software sliding window (wrong subtraction value)

Works, but now needs to be multi-threaded and SIMD-ized.
Delayed I/O data and wren by one more cycle to sync thread with I/O read.

Now I/O writes happen 8 cycles after I/O read, not 7.
Re-implemented using delay_line modules for cleaner code
Scalar Fmax (with attached Accumulator): 468/493/520
Closes #38