Add Feeds support to role reference field.

Same here

This patch adds basic support for feeds. It works in my use case, but I only have one instance of the field on the site I'm using it on.

This also just uses role ids as-is, so if your roles have different ids from the source, some additional changes will need to happen.

Updating nadavoid's patch with a small change to ensure new rids being mapped are not empty, which causes a db error.

Since new values will "always overwrite the target value" according to https://drupal.org/node/1107522 this check seems necessary.

Thank you everybody, for helping. Patch is in the 7.x-1.x branch.