S4L Introduction Mode, Helpers/Tippies

[drniiken]

It would be nice if there was some help when first starting S4L (lite) to guide the user where to find what.

Intel vtune has an approach that is quite nice (see gif):

• first time you select a tab you get some introduction to the main UI features.
• Esc will close this help
• there is a button (always visible) to show it again

A whole number of web-based tools are offering such functionality nowadays. See some more examples attached.

### Watermelon
- [x] Create demo.smash for a Tour @ignapas
- [x] Create some basic helper for first time users @ignapas @odeimaiz

### Sundae
- [x] Present Cosimo with current implementation and come up with concrete use cases
- [x] Extend/refactor capabilities if needed
- [x] Decide on how the backend plays here (guided tours starting projects, projects starting guided tours, etc)
- [ ] Align with oSPARC's Pandy
- [ ] Decide where the definition files will live (external server, each of the apps)
- [ ] Tour creation tool?

[drniiken]

@sanderegg @odeimaiz @mguidon @eofli @calys @drniiken