Allow line breaks in LegislativeLists

Editors want to have multiple paragraphs in a single LegislativeList
entry. In order to allow this, we need to modify the LegislativeList
syntax to have an end tag, and treat everything inside it similarly.

Add $EndLegislativeList tag.
Merge pull request #38 from alphagov/allow-spacing-in-legislative-lists

Allow line breaks in LegislativeLists