Stats update: Preliminary phase

[sbrl]

Stats are a really useful part of any good wiki. We should add more of them, so that people can better see what needs working on in their wikis. This phase of the stats update will deal with a few things in the corners.

• Add the amount of time it took to search
• Add the page index decode time
• Add the search index decode time
• Add the id index decode time
• Add the page index size
• Add the search index size
• Add the id index size
• Add the total amount of space used to store the wiki's data (excluding Pepperminty Wiki's code of course)

The majority of these would make sense on the dev help page, which could do with a bit of tweaking too.