As a User, I would like the Issue Navigator to auto complete users' Email and Username, in addition to their Real Name.

When using the Issue Navigator, I'm only able to invoke autocomplete to assist with completing the user's Full Name, not the Email Address or Username.

Steps to reproduce:

1. Install JIRA
2. Set up JIRA with a new database
3. Create at least one user
   1. Example: username foobar, full name Some Guy, email test@example.com
4. Using the Issue Navigator to search the Reporter field in Basic mode:
   1. Typing Some will invoke the picker with Some Guy as a suggestion
   2. Typing foo will invoke the user picker, but with no suggestions
   3. Typing test will invoke the user picker, but with no suggestions
5. Using the User Picker for Assignee field in Quick Edit will provide suggestions for all three input types
   1. This is the behaviour we expect in the Issue Navigator as well.

Expected behaviour:

• Users will be able to draw suggestions from any of the user name parameters (email, full name, username)