hgweb: replace 'shortlog' with 'changelog' in raw changelog template
hgweb: remove now unnecessary explicit header() and footer()

They became unnecessary after allowing custom-named entries in templates.
hgweb: fix unstoppable loading of graph when no more results

When a user reaches the end of repo history with graph view, it (unsuccessfully)
tried to load more entries. This patch disables further loading attempts.