The separator type is not taken into account when importing

As a reminder the "Assigned" field is for indicating you're actively working on something, after you're done (or if you're not able to get to it) please set the field back to "Unassigned". After four months I'm going to assume you're not able to get to it right now.

Added delimiter field to the metatags import form, update import batch logic.
Added validation of delimiter in import file.
The logic of file's custom upload validator moved to the validation of whole form, otherwise it is hard to
validate delimiter in case when user already uploaded the file and then changed the field with delimiter.
Made validation of import form more complex.
Also i removed translations of exceptions of import batch (according DrupalPractice.General.ExceptionT).

Open MR.

Rerolled.

Committed. Thank you!

Automatically closed - issue fixed for 2 weeks with no activity.