CookieBuilder maxAge should support java.time.Duration

The CookieBuilder maxAge is based on seconds as int, but the contributed default value is using the intermediate type org.apache.tapestry5.ioc.util.TimeInterval which allows for defining an interval as a String.
This makes setting the default quite readable, but CookieBuilder#setMaxAge itself accepts an int and doesn't mention that it's supposed to be seconds.

I propose the following changes:

• Clarify documentation of CookieBuilder#setMaxAge so it's obvious that it requires seconds
• Add #setMaxAge(java.time.Duration)
• Add TypeCoercion Duration -> TimeInterval, so the default value could be contributed as String or Duration, to ensure backward-compatibility.
• Fix the use of the symbol key in the CookieBuilder constructor to use SymbolConstants.COOKIE_MAX_AGE instead of the value