Changes

contrib: restructure REST API usage examples (tryme-scripts)

The so called tryme scripts are using a very clumsy method to set
the varying parameters (tryme.cfg). The files also mix with other
unrelated files in the contrib directory. This patch fixes those
shortcomings.

- put everything related to the usage example into a dedicated
  directory.
- cleanup tryme.cfg so that it only contains one set of parameters,
  add some helpful comments.
- add functionality to pass the the parameters either via
  commandline options or via tryme.cfg, add a parameter to point
  to an alternative .cfg file, so that users can use multiple
  different configurations.
- update documentation
- cleanup other minor inconsistencies

Related: SYS#8100
Change-Id: I4e42ce85c84b47d3561011083da4a1e54958fd8e