do not use angle brackets in hyperlink labels
Fix minor typo in file docs/content/templates/overview.md
taxonomies -> Taxonomies
fix link to template primer
Add PluralizeListTitles option (default true) to allow disabling use of the inflect package
Add shortcode template loading from themes directory.
Allows 404 templates from themes/THEME directories.
report errors

Modify CheckErr and StopOnErrErr to report the error if there aren't any
other messages.
allow site to be built with empty content

Build the site even if there isn't anything in the content directory.