Rename block_device.rb ohai plugin to block_device_extended.rb

Otherwise, it just doesn't work.
Merge pull request #202 from vuntz/fix-ohai

Rename block_device.rb ohai plugin to block_device_extended.rb
Renamed i18n file, added quotes and copyright
Merge pull request #204 from tboerger/feature/i18n-rename

Renamed i18n file, added quotes and copyright