Introduce a new util class for getting client info

This replaces the old ui.core.util.Info class, and allows access
to the version information without going through the config
system.

Change-Id: I4b372b62f6fd5adcfa21f0793ec73df7bf2633b6
Reviewed-on: http://gerrit.dmdirc.com/3120
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>