feature(command-init): netlify functions default directory recommendation

[erezrokah]

The ntl init command recommends functions as the default function directory when initializing a new site.

That might no longer be desired as we support deploying functions from netlify/functions without any configuration.

We should consider removing that recommendation or change the default.

You can see the flow in #1836 (with the added feature of plugins recommendations)

[asavaritayal]

We should keep the recommendation and update it to netlify/functions