Improve `Blame Map`

[ljubadr]

Currently I need to manually get the list of emails and then to add them one by one. For bigger project it's slow and painful task

I'm running git shortlog --summary --numbered --email and I'm getting over 100 results that I need to add manually

Suggestions

1. Add import option where we can add the CSV. For example, each row should be <code autorhed by email>, <now handled by email>

2. Make the email autocomplete from the list of previous contributors. By typing few letters we would get email suggested from the list of all contributors (minus the ones that were already mapped)

[planteater]

Thanks for the suggestion @ljubadr!