Import seeds and Gemfile from feature/rails3.

git checkout opf/feature/rails3 -- db/seeds.rb db/seeds Gemfile
Merge remote-tracking branch 'opf/feature/rails3' into HEAD
Adds migration for legacy journals.

Legacy journals need to be transformed to current journals. This
amazing new migration does it.
Check migration prerequisites.
Adds journal creation to migration.
Extend legacy journal migration

The legacy journal migration now includes normalization into the data
tables. This involves combining previous journals (diffs) into the new
normalized schema and extends to changesets, news, messages and work
packages.
Introduces new migration dated after previous fixes.
Remvoes obsolete migration.
Adds support for more journals.

Now also migrated wiki_content_journals as well as time_entry_journals.
Also, wikis now have some custom behaviour for data -> text conversion.
Adds support for lock_version in wikis.
Adds support for work package attachments and custom fields.

Those are ignored for now.
Introroduces order in journal migration.

This is so that attachments and custom fields are migrated when
workpackages are first touched. It satisfies the need for filenames
when connecting a work_package_journal with attachement_journals trough
attachable_journals, filename being a not null requirement on the
latter.
Adds support for empty changesets.

When just commenting, e.g., a work_package, one can omit all changes,
leading to an empty changed_data object. This is now supported.
Adds support for updates in subsequent runs of the migration.
Moves updates closer together.

Updates can happen really late, and can be wrapped into one call to
execute. This saves about ~25% of execution time on subsequent migration
runs.
Adds support for attachable_journals.
Move migration to a newer timestamp.
Fixes some attachment migration bugs.
Makes one of the update statements optional.

Keys might have been empty for the update previously.