Install and configure oidentd on Eglide

Summary:
IRC uses ident protocol, and oidentd provides an implementation.

By default, the username of the user account is provided, but
configuration allows to change that (blacklisting other usernames).

Ref T1047.

Test Plan:
This part worked:

1. Deploy to Eglide
2. Run a client, see there isn't a ~

This requires a follow-up, or better instructions:

1. Create a local .oidentd.conf override
2. Run a client, see there is this overrided username

Reviewers: dereckson

Subscribers: tomjerr

Maniphest Tasks: T1047

Differential Revision: https://devcentral.nasqueron.org/D707