Viewer OSX doesn't open

The viewer doesn't open on OSX.

To fix it enter pcb-code directory on the terminal and run:
```
chmod a+x viewer/application.macosx/viewer.app/Contents/MacOS/JavaApplicationStub
```

The file JavaApplicationStub needs to have set executable bits.

It looks like Linux chairs the same feed, I didn't test it, but the file
`viewer/application.linux/viewer` is also not set executable.

