Updated 'intro' page

The 'intro' page has been updated to better reflect the state of progress of the L3DT project. Included on that page are three lists:

1. The features in the current release version.
2. The 'to do' list (features I intend to write / am working on).
3. The features that are implemented in my private build of L3DT and will be coming in the next release.

Some may be interested to note that this last list now includes 'painting' tools for the intermediate map. This means you (or rather I) can now paint what you / I want the heightfield to look like. The result is that it is now very easy to design the heightfield - carving rivers or building mountain ranges is a cinch (compare with news item from 10-Jul-03).