improved archive.html template

The archive.html template is now used for yearly, monthly and tags
archives. tag_archive.html has been removed as it's no longer used.
minor code fixes

archive.html makes no use of extra variables "year" and "month",
removed from tpl.render() calls.
Revert "minor code fixes"

This reverts commit 0ffb8ca4a3384f00a52ae10e8884595f91aebec7.
imporoved archive.html template

The archive.html template is now used for yearly, monthly and tags
archives. tag_archive.html has been removed as it's no longer used.
Revert "imporoved archive.html template"

This reverts commit 869dd96bc35159c3594991acf959a33623e1ca0d.
minor design changes