Add IRC gateway solution to OSGeo MatterMost installation

[msmitherdc]

The board is interested it testing out higher end clients that provide more than irc ( slack,Gitter, etc). The solution being tested is MatterMost (​https://MatterMost.osgeo.kbt.io). Now we need to add an IRC connection to support those users that wish to remain on IRC and / or don't want to use MatterMost. One discussed solution is ​https://github.com/42wim/matterircd. While this looks like a decent solution, not much investigation has gone into this so whatever works best from a SAC/infrastructure perspective is fine.

[msmitherdc]

This should also be moved to OSGeo domain and hardware as appropriate

[strk]

Note that Mattermost relies on GitLab for using the OSGeo credentials, so if Mattermost goes prime-time, GitLab should follow it.

[strk]

We are using matrix now for chatting, closing this ticket as irrelevant