Adds support for configuring the default value of derived types' @odata.type property

[irvinesunday]

Fixes #304

This PR:

• Adds support for setting the default value of the @odata.type property in the schema of derived types.
• Adds a new convert setting for setting this default value. The default value is true, meaning the default value will always be emitted. If false the value will be set conditionally based on whether the derived type's base type is abstract (and not entity) and is referenced in the properties of a structural property or an action.
• Updates existing tests and adds a new test to validate the above.

[andrueastman]

Thanks for this!

[baywet]

thanks for taking the changes, one last thing

[irvinesunday]

thanks for taking the changes, one last thing

From the issue description written by @andrueastman, I understood that we should check whether the type derives from an abstract type alongside the other 2 listed checks, else, we generate the default value by default (as is the current current case). Is this not the expectation?

[baywet]

thanks for taking the changes