Better OS X integration

[Don-vip]

Thanks to Stereo I have successfully setup a "Hackintosh" that finally allows me to test JOSM on OS X, in a virtual Machine, by following this guide:

​http://www.macbreaker.com/2014/05/os-x-mavericks-in-virtualbox-with-niresh.html

I find a lot minor issues that I'll try to fix through this ticket:

1. JOSM does not use OS X native LAF by default: fixed in r7480
2. Hyperlinks do not work (left click) if Safari is still the default browser
3. Right click on hyperlinks do not copy the link to clipboard
4. The vertical toolbar is too wide: horizontal space wasted
5. The horizontal status bar is too large: vertical space wasted
6. The icons in preferences dialog are ridiculously small

Many other points to come I think.