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

This reverts commit 4522b7f31b7e753f4e19af60e55633d7c3e0ee52.
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'