CHANGE FEATURE: incorrect x-axis translation should raise an error

[Chilipp]

Summary

If one mark is created for the x-axis translation, the other one should be forced to be in the same column. And it should be impossible to create a mark left from the first column start.

Reason

Better error messages.

Current behaviour

The x-axis translation fails and the final exported result is never translated (without giving any justification to the user)