Introduce a Theodolite Helm chart for deploying all dependencies

Requirements:

• Size of Kafka cluster should be configurable, in particular one-broker clusters should be supported #38 (closed)
• Node selectors should be settable #93 (closed)
• Namespace has to be configurable, if cannot derived from context
• feel free to continue

Special attention:

• Installing Prometheus Operator might be not straightforward as additional rights might be required. Also the user might already have Prometheus Operator operator installed. If there is no other solution, we could simply require it to be installed.