Is Not Installed (Residual config) safe to remove all?

^{As this question merged to here, there is need to provide some information which may helpful}

From man apt-get:

       remove
           remove is identical to install except that packages are removed instead of installed. Note
           that removing a package leaves its configuration files on the system. If a plus sign is
           appended to the package name (with no intervening space), the identified package will be
           installed instead of removed.

       purge
           purge is identical to remove except that packages are removed and purged (any configuration
           files are deleted too).

So, when you remove package(s) usually by using Ubuntu-Software-Center or by sudo apt-get remove, it leaves its configuration files on system.

From community help,

While there is no built in way to remove all of your configuration information from your removed packages you can remove all configuration data from every removed package with the following command.

dpkg -l | grep '^rc' | awk '{print $2}' | xargs dpkg --purge

So, Run following command from terminal:

dpkg -l | grep '^rc' | awk '{print $2}' | sudo xargs dpkg --purge

This will removes configuration files from removed package.

Those listed package are just those that have configuration files that hasn't been removed. Unless you are planning to reinstall the packages again, and want to keep the configuration, yes, you can remove them safely. In synaptic, you can purge them by selecting them all, use the Package menu, then Purge. You can do this from the terminal too:

dpkg -l | grep '^rc' | awk '{print $2}' | xargs sudo apt-get purge