add the grunt-show-config module

added the code directly to our repo, since it contains a new feature.
Once this feature has been merged, it might be possible to use this
module via npm.

This feature is needed, to provide an easy way to generate a local.conf.json
file.
provide an easy way to generate a local.conf.json

Thanks to the nice plugin grunt-show-config, there is a pretty
easy way to get started with a simple local configuration based on
the default.
add first documentation for important tasks

this can be used as a start