Add stride to linebuf and shift reg

[shadjis]

Example stride syntax:

LB: val lb = LineBuffer[T](5, 28, s)

SR: sr(r, *).shift2 ( lb(r, c::c+s) ) { y => y } An alternative syntax we discussed for SR was .shift(s)(...){...}, but only s=1 and 2 should ever be needed, and maybe 4 if it is easy to add

Thanks

[dkoeplin]

Reopening - still needs to be implemented but it's less of a priority now

[mattfel1]

Actively working on this

[dkoeplin]

Syntax for shifting multiple elements in 1 cycle already exists for RegFile:

sr <<= lb(r, c::c+s)

Syntax for strided LineBuffer (added in develop as of 200cd2c): val lb = LineBuffer.strided(rows, cols, stride)