Spawn master, slave, and clusterctl in separate processes in the
clusterio integration tests and leave the test master and slave process
available for the whole test duration to allow plugins to use them as
well. This removes the need for reimplementing the startup logic in the
test code and makes the existing startup code covered by tests.
Replace current configuration mess with a trimmed down version of the
original vision of #200. Configs are collection of config groups that
have fields that can be set. These groups allow organizing the fields
as well as opertunity for plugins to add their own groups. By default
plugins have an auto generated group with the enabled field.
Change Instance class to be a subclass of Link and refactor the
communication to and establisment of instances to use a virtual
connection between the slave and the instance. This is simplifies the
implementation of plugin communication for instances.
Replace InstanceRequest with a forwardTo option to Request which does
the task of forwarding in a much cleaner way.