Improve error message for DataNode

[amuolo]

Due to the current temporary logs pattern, the dimension validation for Data Nodes (and probably also other objects as well) is not shown as the errors captured by the importers are shown before. In other words, the two kind of errors are not merged and one only sees a portion of the total error message. The generalized opinion on this is that this causes confusion.

The aim of this issue is to improve the overall design of logs so as to use activity library.