Unify the execution in code-samples

Find a way to unify how the code samples are executed.

There are some general instructions for executing samples in the `readme.html`, but they are not sufficient for all user kinds. They are targeting advanced/experienced users.

What can go wrong with current structure:
* it's confusing when some samples have bash scripts included and other don't have
* samples don't have Windows scripts, it can look like it's targeting just a Un*x audience

**Suggestion to improvement:**
Avoid using shell scripts and provide README files for all samples.
The READMEs could do the better job than the bash scripts. They should work for Windows users too.

Another improvement could be to employ maven exec plugin, so users would do just `mvn java:exec`. There still would be a need to list the main classes available in the sample in the README.

This issue is related to #188 (instructions how to build the samples).