move settlements into plugins?

[michielbdejong]

if you have several plugins that do pluginVirtual + something, then why does ilp-kit still also offer settlements? for instance, I could create a plugin-paypal, i give it my paypal api key, and every time I owe Evan more than 10 euros, the plugin automatically triggers an unconditional payment over paypal. where is the boundary between a plugin type and a settlement method?

this change would also allow us to focus more on low-level development, without having to also do the higher-level layers of ilp-kit.