Also changes the defaults of questionnaire and answers.

Makes some serializers more terse, and makes unwanted fields read_only.

Adds patching of Deployment's state_target and DeploymentStates
questionnaire (amongst other fields).

The problem is that we deploy Deployment, but questionnaire is bound to
a DeploymentState. To make this work (barely) I added the following
behaviour: Once a user PATCHs a DeploymentStates questionnaire the
DeploymentState is published by acting like it is a ServiceDeployment.
This works as long as the client just executes deployments (and does not
try to gain insight into the backend state by watching the incoming
Deployments)

I'm not happy with this hack.

Ignores groups, when entitlements are present. Closes #22.

Closes #20

With all those strange changes, the migrations were broken. I removed
all of them and started with new migrations.

For django-polymorphic i had to rename the Model 'bases' in the auto
generated migrations, as the seem to be case sensitive.

Also rework the way errors are communicated to the webpage

Makes Deployment and DeploymentState many to many.

The problem is that we don't have deployment 'per service'

Closes #7

Especially adds pending credential states