Fixed #20632 -- Fixed {{ docs_version }} in project template
Modified tutorial 3 to use RequestContext in place of Context.
Fixed error in last commit. Thanks Simon Charette.
Fixed #20630 -- Removed `maxlength` attribute from `NumberInput`.

This attribute is only allowed on inputs of type "text", "search", "url",
"tel", "email", or "password".

Thanks to yoyoma for the report and @bmispelon for the review.