Allow Flux to be deployed on tainted Kubernetes nodes

cmd/flux/bootstrap.go

cmd/flux/install.go

docs/cmd/flux.md

docs/cmd/flux_bootstrap.md

docs/cmd/flux_bootstrap_github.md

docs/cmd/flux_bootstrap_gitlab.md

docs/cmd/flux_install.md

docs/guides/installation.md

pkg/manifestgen/install/install_test.go

pkg/manifestgen/install/options.go

pkg/manifestgen/install/templates.go