Test examples & configuration from the documentation

[bhirsz]

It could be automatic - pull all configs/examples and run the in the isolation and see if they work.

For before/after examples we could try to check also before/after output (but we would need some kind of marker in the docs that would be not displayed but it would show test framework which configuration to use for running the example). Or we could do it in reverse - prepare test files and load examples from them to the documentation (ie. using markers like # START, # END).

From #384