Add config versioning scheme, warn on mismatch

[nyanpasu64]

The separate-peak-and-score branch drastically changes the interpretation of past configs (making edge and slope serve separate tasks, and requiring both edge and slope to be enabled especially if buffer is disabled). This is worth adding a warning when opening past configs in new programs.

Additionally we might want to change the default values in newer corrscope (like disabling DC removal by default or making it mandatory).

Also make sign strength and mean_responsiveness written by default.