Upgrade Installation Process to Helm3

[Neumann-Nils]

Description

This PR upgrades the installation process to helm3. This is also required to be fully integrated into the App Hub.

With the changes of helm3 we outsourced the namespace creation to the user (see https://github.com/helm/helm/issues/5628#issuecomment-545662714). Thus, the installation (without tiller) can be done as follows:

kubectl create namespace karydia
helm install karydia ./install/charts --namespace karydia

An installation in the default namespace is initiated by the following command:

helm install karydia ./install/charts

[Fixes #220] [Fixes #246]

Checklist

Before submitting this PR, please make sure:

• [x] your code builds clean with make
• [x] your code lets succeed unit tests with make test
• [x] your code lets succeed integration tests
• [x] you have documented new or changed features