Migrate command easier for scripting

[ilukac]

added additional argument to migrate command so non-interactive usage is possible.

e.g. to migrate image from "image" field to "remote_image" field in all "ng_news" type of content:

php bin/console_test netgen:ngremotemedia:migrate:ezimage ng_news image remote_image -n

[ilukac]

Btw, if possible merge to adminv2 branch as well.