Ignite: IGNITE_PLUGINS_PATH shouldn't be required

[jamonholmgren]

772 introduced IGNITE_PLUGIN_PATH and required it. However, I don't really think this should be required -- we should infer the path if not found. This results in a bad DX (IMO) when first spinning up an Ignite app.

[skellock]

It was only in place so we can make everything work while in dev mode. The packages will all live on npm.

[skellock]

Just a heads up, this message only appears when the package isn't found on npm.

The resolution order for ignite add something goes like this:

• look for a directory called something (can be relative or absolute)
• look for a directory called something in any path found on IGNITE_PLUGIN_PATH
• look on npm

If all these fail you see that message.

Once we publish ignite-ir-app, we won't see this error anymore.

[jamonholmgren]

I knew that.