Created attachment 275755 [details] [review]
Improve documentation in catalogintro

The pages under the header "Adding Your Custom Widgets" could use the following improvements:
- Grammar edits to improve clarity: For instance, there are a number of run-on sentences that make parsing the documentation rather difficult.
- Cross references: Instead of mentioning that concepts will be explained in the "next" chapter, link to it.
- Improved cohesiveness: It would have helped my understanding if all the documentation under this header referred to a common widget and walked me through modifying the catalog for this widget.
- Improved example: It also would have also helped my understanding if the example widget were something more conceptually familiar, like a TVChannelWidget, instead of something abstract like a FooFrobnicator.

I've started making changes to the documentation that help meet these goals. Comments are welcome.