Notice layer + refactor Interpretation

This adds [S] for section-by-section analyses. This also refactors the interpretations layer to follow the lead of the TOC layer. Almost all existing layers are now "Inline" Layers, while TOC, Interpretations, and Section-by-Section Analyses are now "Paragraph" Layers. 

The results of these layers get added to the node to be available within the template (rather than requiring their own template, as Interpretations used to.)

This pull request relies on https://github.com/eregs/regulations-site/pull/27 ("notices").