[refactor] Renamed Borders to ParagraphBorders (1m)
[improvement] Added pgBorders to sections (5m) [#23c]
[improvement] Added columns for sections (30m) [#23d]
[refactor] Extracted ContainerProperty (5m)
[fix] Added attributes to the columns container (5m) [#23d]
[feature] Added the ability to add sections to documents (10m) [#23q]
[skip] Bumped to version 0.7.0 (1m)