Handle translations

Add a new option -l LANGUAGE to build and publish localized content
that is in generated/$LANGUAGE and copy content to
publish_docs/$LANGUAGE.

Add new option --only-book to build only specific manual.

Read gerrit-doc.properties if exists to pass values to maven.

Change-Id: I6a07fe02428679d0e5e00a4d67f1b11d9c85b262