Add docs for new Data Files feature
Fix typo in data docs; update section pagination for migrations to correctly point back to data
Rebase on upstream/master; rename file to work with docs_ul includes file
another pass on the documentation of generators

This commit refines the docs contributed in f074bb6.
Include tag: provide path in case of render error
Output path in case of render error in included file

Fixes #1591.
Merge pull request #1596 from maul-esel/error-file

Output path in case of liquid error in include file
Update history to reflect merge of #1596
Add parenthesis to the call for super
Merge pull request #1503 from swanson/add-docs-for-data-feature

Add docs for new Data Files feature
Update history to reflect merge of #1503
Merge pull request #1592 from fxn/master

another pass on the documentation of generators
Update history to reflect merge of #1592

Combine it with the entry for #1590 since they're related. Move it
down to the site enhancements section since both pulls are changes to
the site.