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
Update history to reflect merge of #1503
another pass on the documentation of generators

This commit refines the docs contributed in f074bb6.
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.
Move catching of liquid errors in include tags

The previous code only caught render-time errors. This change
makes it catch parse-time errors as well, such as unknown tags.
output correct path in case of liquid error in layout

As with includes, an error in a layout was reported on the
page that used the layout. Fix this by passing on the path
of the layout that is rendered.
Update history to reflect merge of #1601
Add a cucumber feature for variable includes
implement variable retrieval in include tag

Fixes #1464.
Fix code to allow dots in variables
extend feature to ensure it works with parameters as well
Document variables in include tag
Update history to reflect merge of #1495
Update safe_yaml dependency to ~> 0.9.7