Removing removed things

Maybe this helps with the million possibilities I now have
Not adding removed items

Again, is this correct?
Weird empty transformations check

Again, is this right? Might be, who knows...
Put the occurances in the itemSet

Makes a LOT more sense
Keeping the deleted items

Apparently, they are only relevant when computing
the frequency. So, oh well, here they are again
Tightened the condition
A more useful commit message