Add a factory for ActionSubstitutors.

This allows them to be injected with all their dependencies, removing
some deprecated singleton methods or constructor usages.

Change-Id: Ie2960171e29fa4069747ca9a6cd8b427ffc73003
Depends-On: I06b391f62bf6e72b0f24d2dda91e36242564fdff
Reviewed-on: http://gerrit.dmdirc.com/2915
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Update submodules: plugins (new commits)

plugins:
    5c1cdc9 Chris Smith <chris@dmdirc.com>
            Support for ActionSubstitutorFactories.

            Depends-On: Ie2960171e29fa4069747ca9a6cd8b427ffc73003
            Gerrit: http://gerrit.dmdirc.com/2910

Change-Id: If9d26eb4f4ada450da013d6215564b1dc7b876ff