Report: add scrolling on the <tbody>.

With this commit, the <tbody> of the static reports can be scrolled
while the <thead> stays fixed. This has a drawback: when the column is
too large (e.g. a tag --- disallowing a line break --- is longer than
the column should), it breaks the hsync between table header and body.
Report: translate to pure english.
Report: resyle salary filter.
Report: restyle salary slider.
Report: vertically center filters.
Report: horizontally center filters.
Report: minor change on salary range UI.
Report: fix indentation.
Report: recover calendar icons.