Move handling of blit behavior to axes object.
Push handling of line tools to axes level for better coordination.
Remove unused parameter from docstring
Refactor blit manager and event manager to viewer
Switch plugins to use new tool api
Updates to get all tools tested and working
Make other suggested style changes
Add on_scroll behavior and allow line to change width.
Fix failing tests
Merge pull request #1065 from blink1073/multi_linetool_drawing

Multi linetool drawing