browse page: improve css for h4 headings

 - give more room for content
 - make less clunky overlaps when not enough room
browse page: collect "download xml" & "edit" links w other right-hand action links
browse page: collapse "last edited" info rows into a sentence under the heading
browse page: float browse-nav to right-hand side
browse page: less wordy headers for changeset content panes
browse page: express last-edited time as user-friendly "time ago"
browse page: undo my mistaken reordering of divs

(fixes a clear:both issue on small screens)
browse page: no top-border-bar for first child needed now
browse page: better way of specifying "time ago" (for i18n)
browse page: more approachable headings

(involves slightly rejigging the way printable_name() invokes i18n)
browse page: ensure neat render (no spurious top bar) when no-tags-no-comment
browse page: formatting tweaks for small-screen mode
browse page: printable_name() opt args converted to named hash options
browse page: full rather than "lego" i18n strings for editsummary
browse page: reinstate version metadata on history page
browse page: remove title translations that are now no-op
Merge remote-tracking branch 'danstowell/browsepage' into next