Fix typos in documents and comments

Fix typos detected by toolkit misspellings.

* pip install misspellings
* git ls-files | grep -v locale | misspellings -f -

Change-Id: I3d7c06bcc3b5d0cdf82b8da98a7fba15e935cab6
Merge "Fix typos in documents and comments"
Improve pecan documentation and correct intersphinx references.

Change-Id: Iac6229a2727a3c662d3fe9e83e1aa02ef648f025