feat(webhooks): add webhooks to user.preferences (API settings) so we can post to external services (eg, Beeminder)
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
Added uuid parameter to data link
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.
fix(paypal): charge "immediately" for on subscription setup
fix(hall): remove global vars
fix(payments): allow resubscription after unsubscribe
feat(help): add tour to help menu
feat(invite-friends): obfuscated invite
Merge pull request #4253 from HabitRPG/obfuscated-invite

feat(invite-friends): obfuscated invite
feat(quest): Add owl to purchasable quest eggs
Merge pull request #4255 from SabreCat/owl

feat(quest): Add owl to purchasable quest eggs
bailey(owl)