Fix up some DB migration issues with Rails 3
Fix up some DB migration issues with Rails 3

* The public_body_tags table had already been removed
* The index has_tag_string_tags generated a name longer than the Postgres maximum of 63 characters. It was ignored in earlier Rails versions, see: https://rails.lighthouseapp.com/projects/8994/tickets/6187-postgresql-and-rails-303-migrations-fail-with-index-name-length-64-chars

obshtestvo/alaveteli-bulgaria,petterreinholdtsen/alaveteli,obshtestvo/alaveteli-bulgaria,Br3nda/alaveteli,TEDICpy/QueremoSaber,Br3nda/alaveteli,petterreinholdtsen/alaveteli,TEDICpy/QueremoSaber,andreicristianpetcu/alaveteli_old,datauy/alaveteli,nzherald/alaveteli,10layer/alaveteli,codeforcroatia/alaveteli,TEDICpy/QueremoSaber,Br3nda/alaveteli,petterreinholdtsen/alaveteli,10layer/alaveteli,petterreinholdtsen/alaveteli,Br3nda/alaveteli,codeforcroatia/alaveteli,andreicristianpetcu/alaveteli_old,4bic/alaveteli,4bic/alaveteli,obshtestvo/alaveteli-bulgaria,codeforcroatia/alaveteli,10layer/alaveteli,TEDICpy/QueremoSaber,nzherald/alaveteli,andreicristianpetcu/alaveteli,andreicristianpetcu/alaveteli,andreicristianpetcu/alaveteli,4bic/alaveteli,Br3nda/alaveteli,andreicristianpetcu/alaveteli_old,nzherald/alaveteli,datauy/alaveteli,TEDICpy/QueremoSaber,nzherald/alaveteli,4bic/alaveteli,petterreinholdtsen/alaveteli,andreicristianpetcu/alaveteli_old,andreicristianpetcu/alaveteli,4bic/alaveteli,andreicristianpetcu/alaveteli,datauy/alaveteli,obshtestvo/alaveteli-bulgaria,andreicristianpetcu/alaveteli_old,codeforcroatia/alaveteli,obshtestvo/alaveteli-bulgaria,nzherald/alaveteli