REL: v3.5.1

This is the first bugfix release of the 3.5.x series.

This release contains several critical bug-fixes:

• fix installation issues when setting a default backend
• fix add_lines on horizontal colorbars
• fix streamplot with start points on right or top edge
• fix colorbars with boundaries or NoNorm
• fix colorbars with negative contours
• fix colorbars with tight layout
• fix setting Axis label alignment to center
• fix subfigure tight bounding box
• fix subplot parameter window on macosx backend
• fix unit handling in Collections.set_offsets
• fix unyt integration in errorbar
• re-display date offset in ConciseDataFormatter after zoom
• reduce do_3d_projection deprecation warnings in external artists