Runtime configuration for the kukit javascript

We will need some configuration for the javascript.

Things that would go there:

- setup of constant values, for example global queue manager response timeout

- switches for 3rd party modules, ie. currently we decide if we want to use cssQuery or base2 for querying css selectors based on which library is present, but it would be desirable to set this up explicitely.

This is strictly separate from plugins or application level setup and has no interference with plugin or application level.

In any of the supported server platforms, we would allow a way to set up these values from the environment (i.e. utilities from Zope, etc), but this is already a next step.