Improve saas + rest-api starter

[jondot]

• Organize route generation: Organize which routes are prefixed with "/api" #818
• Create default initializer hook, with the standard view engine Create default initializers #509
  • make sure lightweight template has no initializers (override with empty)
• Remove notes.rs, move user.rs profile into /auth/current (which makes user.rs removable and remove it.). after this, controllers/ folder has only mod.rs and auth.rs see also Clean Starter #820
• Add to starter generation option "API" along with "client side" and "server side" asset serving. API option will set up NO asset serving

After these steps saas and rest-api starters will be similar, and we can remove one of them, call the new starter app.