Update cakin Indigo how-to documentation for package.xml format 2

Almost all of these changes will also need to be applied to the ``groovy-devel`` branch used for Groovy and Hydro.

I want to get review approval before merging them there, so let's just focus on the ``indigo-devel`` branch for now.

For preliminary discussions, see: #440

Formatted version here: http://farnsworth.csres.utexas.edu/docs/catkin/html/