ProjectExplorer: Make RunConfiguration::fromMap() public.

Callers might want to use it polymorphically, e.g. in the restore()
method of a factory that can create more than run configuration.

Change-Id: I773f7b5d75fb6f9ad007cdafc0cf0b56e5f8da8b
Reviewed-on: http://codereview.qt.nokia.com/4266


Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>