- Remove "Export HW Ports" button
- Make the "Export Ports" checkbox apply changes immediately
- Change the status label to show when ports are exported

When stopping jackd, ensure that a2j is actually started before
attempting to stop it. Otherwise we get an error and jackd is not
stopped.

Signed-off-by: Alex Tsitsimpis <alex.tsitsimpis@gmail.com>

- Fix 'Export HW port' tray option not working and incorrect state
- Disable 'Export HW port' when ports are already exported and notify it
with the button text
- Do not start A2JMIDI after exporting ports
- Stop A2JMIDI before stopping JACK

- Add option to start a2j when JACK starts
- Add option to always export ports when a2j starts
- Remove now unused a2j options menu
- Remove unneeded HW export yes/no dialog and automatically (re)start a2j after exporting

Closes #209