Ensure the application is always started in the APP_HOME directory

When using the `application` plugin to build a distribution, the startscripts that are generated should ensure that the application is started from the `$APP_HOME` directory.

It will then make no difference whether the application is started as:

    APP_HOME %> bin/myapp

or

    APP_HOME/bin %> ./myapp

or even

    / %> APP_HOME/bin/myapp

All relative paths in the application will then work correctly regardless of from where the application is launched.