It might look a bit odd, but what about circuit diagram type software? That would fulfill most of the requirements you mentioned. How about TinyCAD? http://www.google.co.uk/url?q=https://sourceforge.net/projects/tinycad/&sa=U&ved=0ahUKEwie_7rsiOfSAhVkDcAKHSKNBIsQFggSMAA&sig2=1_xs3rwPDtlLQ98oE_XABg&usg=AFQjCNGO0XhmY-Bd6gwUrhew0a4FY36BsA

It might look a bit odd, but what about circuit diagram type software? That would fulfill most of the requirements you mentioned. How about TinyCAD? https://sourceforge.net/projects/tinycad/