Migrate first_name, last_name to realname, fixes T160

Summary:
- update controllers, models, api, and tests
- update client js and html
- update base.yml
- update import2x

Test Plan:
```
lang=sh
for feature in $(git diff master --name-only -- application/tests/features); do
    ./bin/behat --config application/tests/behat.yml $feature --format progress
done
```

Reviewers: rjmackay

Reviewed By: rjmackay

Subscribers: lkamau, dkobia

Maniphest Tasks: T160

Differential Revision: https://phabricator.ushahidi.com/D62