Explain what Fluent and Leaf are during setup

[BrianHenryIE]

I was setting up Vapor for the first in a few years and didn't know what functions Fluent and Leaf were. For beginners, the setup wizard cannot be completed without trips to Google to learn more. This PR inlines what the tools are used for.

Before:

Would you like to use Fluent? (--fluent/--no-fluent)
y/n> n
fluent: No
Would you like to use Leaf? (--leaf/--no-leaf)
y/n> n
leaf: No

After:

Would you like to use Fluent (ORM)? (--fluent/--no-fluent)
y/n> n
fluent: No
Would you like to use Leaf (templating)? (--leaf/--no-leaf)
y/n> n
leaf: No

[0xTim]

Thanks!