k4 dictionary operations

[bakul]

  x:`a`b!1 2
  y:`a`c|4 6
  x+y
`a`b`c!5 2 6
  x*:3
  x
`a`b!3 6
  x,y
`a`b`c!(1 4;2;6)

If a key,value pair exists in both operands, the operation applies to the value. If the pair is in only one dictionary, the key is added and the "right" thing is done (probably by adding the correct default for the operation). For instance:

  x-y
`a`b`c!-3 2 -6