[make links] to set up symbolic links for debug

[jankeromnes]

Create a make links target for lightweight development and debugging.

Advantages:

• Doesn't duplicate plugs and meta folders
• Your modifications are directly committable to git

Drawbacks:

• Exposes .git, .gitignore and meta in web, which creates recursive metadata that you don't want to commit.

[jankeromnes]

Also rebased to garden/master, @espadrine please merge when your internet gets better :+1:

[espadrine]

LGTM