errors vs validate::errors

[edwindj]

We have a slight semantic name clash with validate::errors.

In validate, errors is a generic function for detecting rule evaluation errors. In locate_errors the term "error" is used for invalid values of observations. The result of locate_errors is an errorlocation object that has a slot errors (a logical matrix)

This has not been a problem (only an inconvenience), but I am in doubt of implementing the errors method on the errorlocation object. That would be really confusing for the user... @markvanderloo any ideas/suggestions?