Due to the yanking of imgui-winit-support 0.6.1, builds that did
not have a lock file started failing in places. I've now locked
the versions of imgui and friends to exactly 0.6.0 to avert those
issues for the time being, with the longer-term fix being the
upgrade of all those to 0.7.0 in #13.
- This commit also fixes an issue with legend rotation and orientation
always being set to values even if the user did not specify any.
This broke the interactive configuration of where the legend should
be.
