Revert "Add 5.20 to Travis CI builds" as it looks like Travis has issues with 5.20

This reverts commit 4522b7f31b7e753f4e19af60e55633d7c3e0ee52.
Remove erroneous min limit from xy_size_compensation definition. #2096
Initial work for custom bed shape
Liquid resizing of plater
More incomplete work for using bed_shape in plater
Finished implementation of bed_shape in plater
Incomplete work for adapting wizard to bed_shape
Finished implementing bed shape configuration within wizard
Handle legacy configs
Revert "Add 5.20 to Travis CI builds" as it looks like Travis has issues with 5.20

This reverts commit 4522b7f31b7e753f4e19af60e55633d7c3e0ee52.
Merge branch 'bedshape'
Add support for circular bed
Removed print_center option (but left --print-center from CLI)
Fix harmless typo
Add support for custom bed shapes
Set preset dirty after setting bed shape
Added non-uniform scaling commands to the plater
Bugfix: object steps were incorrectly invalidated. #2102
Assign category to dont_support_bridges
Fix the Change Scale toolbar button