Shape-Out 2.0.0a27

• feat: add developer mode
• feat: display images on hover in polygon window in QuickView
• feat: implement loading of (polygon) filters from file
• feat: implement session saving and opening
• feat: added perceptive colormaps and set viridis as default
• feat: allow to set hue range for feature-colored scatter plots (#1)
• feat: add colorbar (#1)
• fix: hide confusing "Advances Export" plot menu in developer mode
• fix: only show scalar features in QuickView feature selection
• fix: QuickView -> Event -> Features labels in table were drawn
  on top of each other
• fix: minor redrawing issues
• fix: AttributeError when removing a plot on macOS
• fix: increase maximum size of plots by factor of 100
• fix: editing a polygon filter deselected it from the filter
• enh: Increased speed in QuickView when scrolling through events
• enh: Added pyqtgraph version check