DVCS Integration For Gitlab should support User Accounts in addition to existing Groups Functionality

Issue Summary

Gitlab integration currently only supports adding Groups in the configuration. It would be nice if this functionality also supported the option to use a User account as well. There's even an API for it:

https://docs.gitlab.com/ee/api/projects.html#list-user-projects

Steps to Reproduce

1. Navigate to Administration > DVCS Accounts and click "Link an account"
2. Toggle "Host" field to GitLab Self-Managed, or GitLab.
3. Observe that the field you need to input a Group has the text of "Team or User Account".

Expected Results

An option to toggle to user based connection which would switch from groups to user api backed calls to Gitlab.

Actual Results

The field expects a Group account.

Workaround

None.