Provide services for eggdrop

Summary:
Compatible only with FreeBSD.

The rc service provided has an instances parameter to write all
the eggdrop names, so a unique service can be used for all of them.
The code is based on the MySQL FreeBSD port instances handling.

service eggdrop status will get an overview of all the eggdrops
in one command. It also allows to run them at reboot or stop it
as once.

Ref T1309

Test Plan:

• service eggdrop status
• service eggdrop status Wearg
• TC2 has been launched through /usr/local/etc/rc.d/eggdrop start TC2

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1309

Differential Revision: https://devcentral.nasqueron.org/D1236