#588 page-bars independent height via conf-setting

[tokyoahead]

I am not sure about the average web, but if you do not explicitly
filter out graphics to count as hits, you probably have about 5, or
even 10+ graphics per page.

This however makes the page-bars very small in display since the
height-max is relative to the hits-bars.

I think this should be changed or at least made configurable with a
conf-setting.

A page-bar only at 10% of the bar height is not very usefull. beeing
that the highest of all page-bars make graphical comparison
impossible.