Form Generator: SWT support

For the next release of Metawidget (v0.95), I'm going to have a go at some (long overdue) SWT support.

SWT is notorious for being difficult to work with for dynamic UIs. This largely seems to stem from the fact a Control cannot be created independent of a Composite (container): you have to specify a Control's Composite at construction time, so you can't easily remove it from a Composite temporarily, or move it from one Composite to another (eg. from outside to inside a TabFolder).

I got a huge leg up from Stefan Ackermann, who implemented a partial port of Metawidget to SWT for me, so things aren't going too bad so far. An alpha build is in SVN.

But it's early days yet. Any SWT experts who would like to lend a hand (coding or testing) are very welcome!