Improve --typechecked help text

[jrodewig]

Ticket(s): FE-###

Problem

The following isn't clear for the --typechecked help text:

• For top-level databases, typechecking defaults to true if --typechecked is unspecified.
• For child databases, the database inherits typechecking from the parent DB if --typechecked is unspecified.
• You can disable typechecking with --no-typechecked.

Solution

Edit the --typechecked help text for clarity.

Result

Fewer surprises when creating databases.