Slice Assignment-like methods for FSArrays that dont' require getting the size exactly right

[thomasballinger]

Often you want to slam an FSArray content into another FSArray arr but you don't want to figure out exactly the dimentions; you just want to

• place the top left corner of content at a row/column location in arr, and cut off the content if it gets too big
• place the top left corder of content at a row/column location in arr, and wrap content if it gets too big
• place teh top left corner fo content at a row/column location in arr, and extend arr if content gets too big

We should have methods for these.