Default `application_home` is not a good general choice

The name of the application is selected by looking at the enclosing directory of the main script: https://github.com/enthought/traits/blob/66b57b7c1f2127fc070fa943773c840f5f44a9ca/traits/etsconfig/etsconfig.py#L361-L383

This is often something generic, like `app`, or when being run in tests is likely to be the name of the test runner (eg. `unittest`).

The only way to override is to completely override `application_home`.

Having a property that can be set for the directory name would be very useful.