#305 Open in default system application

[Terry O'Neill]

Java version 1.6 and later allows for easy opening of files and URLs in the default system application using the Desktop API. We should be taking advantage of this and at the minimum:

- Replacing use of the BrowserLauncher library in the Website plugin.
- A fall-back for failure of the "Open in OpenOffice.org" for office normalised documents.

The other areas this would be useful is:

- Opening files that have only been converted using the "Convert" functionality and hence are not xena files
- As a general option for all xena files probably shown next to "Export" (At this point it may be worth removing the "Open in OpenOffice.org" button altogether)