Setting chdir to application directory. 

The _execution directory_ is now the _application directory_

* Logs get placed relative to the _application directory_ not to the `bin` directory
* `RUNNING_PID` file gets placed in the _application directory_ not in the `bin` directory

This makes the behavior consistent to former play versions.

## Additions

I will provide another commit in this pull request with the following addition:

* java_server_application in Debian will created a directory `/var/log/<application>`
* java_server_application in Debian will created a symlink `/usr/share/<application>/logs` to `/var/log/<application>`

With this, logging will be put in the right place *without changing* the default play logging configuration.
Furthermore the debian purge mechanism should remove all folders correctly.