Change the prefix of sub modules from document-validator into redpen

- change sub module names
- change the names of result artifacts
Add "target" into .gitignore
Replace document-validator into redpen in the file names and UIs

- replace command name from docvalid into redpen
- replace file names, documentvalidator.css (.js) to redpen.css (.js)
- replace document validator in UI.
Merge pull request #147 from takahi-i/rename-sub-modules

Great! Merged!