Many users complained that the reflowing process is too slow. This is
rather a speed-quality dilemma. Trade-off can be made by decreasing the
dpi of source page. And by default quality is prefered.
By default the indentaion detection is enabled in K2pdfopt. This will
sometimes generate very poor reflowed page when there are sidenotes on
the page which would be treated as indentation. Disabling indentaion
detection will rescue the reflowed page from this situation.
For now only line spaceing and word spaceing are configurable with
'F'/'Aa' commands. And device size are passed to k2pdfopt in place of
the hard-coded default width and height(via @dpavlin).
