Changed
* Series.get_roi_mask(): Return 2D mask when original images is 2D.
* Viewer: Display image text even when some attributes are missing.
* Viewer: Better presentation of window center/width when they are floats.
* Viewer: Reimplemented PageDown/PageUp to scroll one page at a time.
* Viewer: Adjusting window center/width is modified to use
series min/max, not existing window.
Will improve user feedback when window is unreasonable.
Added
* Viewer: Ctrl+Home/End will scroll to first/last series.
* Viewer: Ctrl+Array Left/Right will scroll one series.
* Viewer: Ctrl+Array Up/Down will scroll one row of series.
* Viewer: Toggle the hide text will affect all series.