Commiting Ana-Maria Constantin's work on the "Telescopes" section of
the Astroinfo project. While I still have improvements to suggest and
maybe even some corrections to make, I thought this work could get
commited since it was already usable.

Thanks Ana! I hope we can polish this work a little more before we
close this task.

Note that I made a couple of changes to Ana's docbook file -- I fixed
a couple of syntax errors, and a small typo that prevented it from
compiling.

In addition to that, I also added the new article into the
indexes. I've created a new section called "Instrumentation" to adopt
this article under the Astroinfo project.