expand capabilities of hey kill

[masukomi]

hey kill <type> <id / name>

E.g.

hey kill tag foo
hey kill person foo
hey kill event foo

AND support last still

hey kill last <type>

for tags and people there can be multiple in the last so it would report back with something like

Please specify which person:
hey kill person bob
hey kill person barry

This also means hey kill <person name> functionality would have to go away. hey kill person x still kills all events with only them in it, but hey kill tag x only kills the tag. It's acceptable to have an untagged event

[masukomi]

related issues #5 #13