This commit makes sure that the `.Site.LastChange` is fetched from the latest page modification date.
Previously, this value was fetched from the last page in the default page sort, which may not be the last by date
if weight is set.
Fixes#2909Closes#2910
Note that this looks like overkill for just the logger, and that is correct,
but this will make sense once we start with the template handling etc.
Updates #2701
This includes removing the error return value from Permalink and RelPermalink.
We ignore that error all over the place, so we might as well remove it.
Updates #2297
To make it easier to follow and understand.
Both building and rebuilding now follow a four step flow:
1. Init
2. Process
3. Assemble
4. Render
And now there are only one Build method, used for both builds and rebuilds.
Updates #2297
