ignore generated dictionary and package files
remove unneeded wildcard from .gitignore
add README files copied from Itadaki wiki

Copy all of the pages from the Itadaki wiki (saved by the Wayback
Machine) into README.md files. Not all of the modules had a wiki page,
so not all of them get a README file. Combine intro, installation,
building, and overview pages into the main README file. Edit links
and comment where necessary (especially to attribute source or provide
new contextual information for this repository).