*8190* fix URL encoding for DOIs

This validation is only used in the NativeImportDom, when importing pubIds. 
I am not sure if the DOIs could be checked usefully/meaningfully? 
The syntax of the DOI string is: <DIR>.<REG>/<DSS> Maybe then just something like this: ^10\.\d+\/ ? Although I am not sure if <REG> could only contain numbers? What do you think?
Else, I would maybe remove this check?