Refactored Wire and finally renamed length to width

Note: since this change was prolonged for some time, so it needed to be changed in a lot of places. The reason for the renaming is the confusability with the length of a (e.g. physical) wire. But it is more precise to call it (bit-) width, since the length of a BitVector passing through the wire becomes its width. (This seems to be similar named in Verilog)