Separate policies into different files

[Floppy]

This is a structural thing. We've wondered before about having one file per policy, and it's been tried in a side branch or two before.

Advantages are that you could:

• tag one policy with multiple areas (for instance, energy and environment) to show it in different pages
• have structured metadata per policy (like timescale #406)
• references wouldn't need renumbering every time, we'd merge them in intelligently (somehow)

Editing system would need to be slightly more complex to link to the right place for each policy to be edited, but it would be simpler for users. We'd also need a button for "create a new policy". The editor would need to be more customised to allow tagging and editing of metadata.

This would allow some rather cool stuff further down the line as well in terms of vote delegation, as it's the only way to allow rich tagging of individual policies.

[Floppy]

I've got the rendering and editing side pretty much working; only thing needed is editor support for new policies, as well as probably some way to remove.

[Floppy]

The editor can now create new files easily, so this is much more in reach.