Change default operand namespace to shipwright

[adambkaplan]

Currently the operator installs the Shipwright build controller into the shipwright-build namespace.
As the project grows, we may add more components that could/should be installed in the same namespace as the build controller by default. By way of comparison, tekton's operator installs components into the tekton-pipelines namespace by default, even though this project has grown to include more components (triggers, dashboard, soon chains and results...).

From #10 (comment)