Associate/Dissociate commands

[ehharvey]

We want to be be able to associate/dissociate items together. For example:

1. WorkItem to/from Blocker
2. Tags to everythinig

Previously, we've just done this via create and edit, and this did work for 1-1 relationships.

Tags are more complicated. A single tag could be associated with 100s of items, so it's not feasible to use edit to update this list entirely. This approach would also cause issues down-the-road when we get concurrent users.

I'm thinking of new commands, associate and dissociate, so that client requests are coming in as 'add an association' or 'remove an association', which is different with a request like 'here is the new list of associations'