Experimental Rudder implementation

Added tests for --repo flag for helm fetch command

Added make target
Lowered docker image sizes
Updated ruder.pb.go

Extracted delete specific code from ReleaseServer to external function
which is called from both Local and Remote ReleaseModules.

Made getVersionSet function from tiller package exported.

Both local and remote Release module implement release status check.

Added dockerfiles for rudder service and tiller run with
--experimental-release flag

This change introduces the concept of Rudders - pluggable modules that
Tiller communicates with via grpc, which allow to decouple orchestration
logic from Tiller into separate service.

This commit consists of simple Rudder implementation which does exactly
the same thing as built in Tiller orchestrator - it creates all k8s
objects from provided manifest without orchestrating them.

--experimental-release flag is introduced to enable this behaviour.

This change allows to use the service and tiller outside of the cluster.
Following commits will add Rudder to helm deployment.

chore(helm): fix go style issues in completion.go

Remove warnings about hook ordering guarantees

With hook weights, execution ordering can be built.

Update download links in README.md from v2.4.0 to v2.4.1

fix typo: ' instead of `

fix(helm): reverted upgrade of imdario/mergo

    Reverted the version of mergo to a version that was known to work
    with both kubernetes and sprig.

    Closes #2376

- [ ] Added tests for --repo flag on `helm fetch` command
- [ ] Also added tests for (pkg/repo).FindChartInRepoURL

Implements --repo flag to commands fetch, install, inspect, upgrade

chore(tiller): bump Sprig to 2.11.0

This adds the `merge` function, among other things.

fix(releaseutil): remove newline on SplitManifests

fixes #2158

fix(create): incorrect URL in default NOTES.txt

Return as not ready if it new RS is nil

fix(*): handle unreleased versioning

Releases are locked to avoid parallel changes