feat(webhooks): add webhooks to user.preferences (API settings) so we can post to external services (eg, Beeminder)
fix(mods): restricted projected fields for mods-listing. Also,
static-bind for perf
fix(paypal): move from classic paypal APIs to paypal REST SDK
Merge pull request #4244 from HabitRPG/paypal2

fix(paypal): move from classic paypal APIs to paypal REST SDK
fix(config): switch to new config style for emails, cc @lefnire
fix(invite-friends): generate correct link on the client
fix(paypal): don't crash server when no paypal plan.id (see #4246)
refactor(paypal): move billing plan setup to a one-time file. It needn't
be called every server-run (see #4246)
refactor(payments): cleanup into directory, separate paypal & stripe files
Merge branch 'webhooks' into develop

Conflicts:
	src/controllers/user.js
feat(webhooks): move webhooks from array to object (everything should
really be stored as objects). Add to API routes (see
HabitRPG/habitrpg-shared#83a22b8). Note, sorting doesn't work. Meh.