Changes include:
  * new parameter "no-ipv4-frontend" to prevent the request of an ipv4 frontend. The webrunner cannot provide one, so let's get rid of failing promises.
  * new paramaters to define the ports of the ssh servers (for runner-importer and runner-exporter). Then no colliding when servers run on the same IP.

Revert "slaprunner: fix resiliency test, add development-mode (bool) parameter for easy build webrunner in webrunner"

This reverts commit 59966611.

hosts-dict values cannot be domain names.
memcached entries are implementation-independent (no mention of kumofs
anymore).
relational database information (which does not follow above memcached
rule, sadly, naming mariadb explicitly) is published in two lists.
Add minimal patterns to document what requester should expect.
Document deadlock-debugger-password".
Drop non-standard "optional" property from jupyter-url declaration.

slaprunner: fix resiliency test, add development-mode (bool) parameter for easy build webrunner in webrunner