Read-only runcards objects

[alecandido]

Runcards objects should mirror exactly the user input.

E.g. Rotations in OperatorCards contains a lot of members that should never be set by the user, and are only modified later on. This should definitely fit somewhere else.

Let's review this objects as soon as possible. They should also not be loaded from dictionaries containing leading _ keys.

@andreab1997 provide your feedback about the new runcards.

• drop Rotations (just keep xgrid top-level) - done in Change manipulate to act on Operator #292
• make the dataclasses frozen=True (avoid mutating them)

[felixhekhorn]

Note that #183 is related