Flipping chromosome start/end in plotIdeogram

[sarmapar]

Hello!

@toobarashid96 and I were wanting to put an ideogram along the y-axis of a square hi-c plot, but we realized that the vertical ideogram is flipped respective to the hi-c axis (see attached plot). We would like to request the addition of a "flip" parameter to plotIdeogram to allow for flipping the ideogram so the end is before/above the start.

example plot

[nekramer]

Those pesky Hi-C plot orientations strike again! Thank you guys for suggesting and implementing this <3