Split topic and activity

[neithere]

Currently I have to write things like {activity: argh, category: foss}. This in nonsense.

The right way is something of this kind: {activity: develop, project: foss/argh}.

[neithere]

The situation has changed to something like {activity: code/foss/argh}. This is better but {activity: develop, project: foss/argh} would be still optimal.

The issue somewhat depends on Diary←→PIM integration (or maybe not — if dumb string matching is enough).