Edits to docbooks

Hi Vladimir,

Here's a complete edit pass on the docbooks to help with 1.0. Generally my changes correct typos/misspellings, a few style issues, and in cases where I understand the functionality well enough and it seemed like something could be misunderstood, I clarified.

I'm not exactly sure how these XML files are typically compiled, so please check me on that. (But hopefully risk of error is low; I didn't change any of the markup, just existing text.)

Wade