Save to image fix (ticket:96)

  * ImageSaveDialog now uses a SequenceBrowser copy contructor to draw the image.

  * glseqbrowser copy constructor was missing path_segments.

  * SequenceBrowser now has a copy constructor.

  * ImageSaveDialog needed to updated to use the bp per pixel zoom magnification;
	meaning that when the user wants an image twice the x value of the glcanvas,
	then the bps per pixel needed to halved.

	  * bp_per_pixel2 = ( x_1 / x_2) * bp_per_pixel_1