[General] Launch page for Screencasts

[Mimi Yin]

I've pulled together a launch page for the screencasts, linked from  
the Features page.

Demos Page:
http://chandlerproject.org/Projects/PreviewDemos

Features Page:
http://chandlerproject.org/Projects/Features

Please review.

It includes a brief glossary at the top and more descriptive titles  
for the movies as promised.

Are there terms missing from the glossary? (This abbreviated glossary  
should probably link to Pieter's more complete glossary in the Get  
Started Guide.)

(The stills and text don't link to movies because we don't have a  
final hosting solution in place yet.)

Mimi