improve tooltip
put "close" and "more..." button in upper right corner,
rename "more..." to "open in pager", add expand button.
tooltip don't have scroll bar an are 'small' until pressing "Expand"
they then change their height and add scrollbars.
Horizontal scrollbar behaviour seem to depend on the browser
>>> plot(<tab> and then click on "expand" :
Firefox : no horizontal scrollbar (wrap line ?)
Chrome : horizontal scrollbar
beware that don't limitting tooltip height or width through css will sometime give
tooltip that are too heigh and will overflow below the bottom of the screen
animation are broken with max-height and/or min-height