trivial docu fixes

Good day Nico!

I've fixed half a dozen little typos, asciidoc syntax gotchas, slighlty improved wording (at least IMHO). Please have a look at the diff and in case it's OK, then please merge it in (pull..).

I'll try to improve the explication of how dependencies work in the manifest docu next, that's why I'm asking you to pull now, because the work that will follow now will be different in character.

Greets!
*t