Convention for calling filter plugins not followed in all files

[YoshuaNava]

Hi,
I'm a user of the filters, and after switching to ROS Melodic I'm getting warnings about the laser filter files not specifying the parent owner of their plugins.

An example:

Bad filter type ScanShadowsFilter. Filter type must be of form <package_name>/<filter_name>

I've checked the files in your repo, and noticed that one of the yaml files complies with the <package_name>/<filter_name> convention, while most of the other files do not.

Indigo is EOL in a month, and I think this package should remain compatible with newer versions. Hence, it would be good to update these files. I'll submit a PR with the relevant changes.