add function to build multiline geoms from relations

needed for waterways in gazetteer output,
fixes https://github.com/twain47/Nominatim/issues/133
add libbz2-dev for ubuntu installs
Merge pull request #149 from smathermather/patch-1

add libbz2-dev for ubuntu installs
Update README

Fixes typos in the README
Merge pull request #150 from ahutchings/master

Update README