Use of lastBuildDate makes output non ideponent

[ssbarnea]

Because the rss.xml is using lastBuildDate which always change all xml files are recreated and thus needing deployment.

That date should be the date of the last commit instead of .Date.Format which varies too much.

Building site twice should not report any changed files.

Another idempotency breaking comes from sitemap.xml where order of seems not to be consistent, at least for the categories, where I seen random changes. Probably cased by an unsorted dictionary.