Quicker access to last changes on a Wiki page

[Christian Boos]

I propose to add a new local navigation link for the wiki, called Last Changes, which would go to the diff view for that wiki page, diffing between the last 2 revisions.

This would be a shortcut to Page History / View Differences.

Also, this would be consistent with the Browser's Last Changes link (currently only avaible in the TracDiff branch).

A corollary to this change would be to removal of the Recent Changes link, which can currently be easily misinterpreted as providing the same functionality as the one suggested above for Last Changes. Instead, the Recent Changes links to a kind of restricted Timeline, which is somehow redundant with the true Timeline.