Split off cli into separate binaries (#37)

* 🎨 Split off cli into separate binaries

This commit splits off the cli into 3 binaries:
- agent
- cli
- provider

The provider now is a separate component that can be tested by itself
and have its own lifecycle. This paves the way to a ligher c3os variant,
HA support and other features that can be provided on runtime.

This is working, but still there are low hanging fruit to care about.

Fixes #14

* 🤖 Add provider bin to releases

* ⚙️ Handle signals

* ⚙️ Reduce buildsize footprint

* 🎨 Scan for providers also in /system/providers

* 🤖 Run goreleaser

* 🎨 Refactoring

.goreleaser.yaml

@@ -10,9 +10,34 @@ builds:
     goarch:
       - amd64
       - 386
-    main: ./cli/
+    main: ./cmd/cli/
     id: "c3os"
     binary: "c3os"
+  - ldflags:
+      - -w -s
+    env:
+      - CGO_ENABLED=0
+    goos:
+      - linux
+      - windows
+    goarch:
+      - amd64
+      - 386
+    main: ./cmd/agent/
+    id: "c3os-agent"
+    binary: "c3os-agent"
+  - ldflags:
+      - -w -s
+    env:
+      - CGO_ENABLED=0
+    goos:
+      - linux
+    goarch:
+      - amd64
+      - 386
+    main: ./cmd/provider/
+    id: "agent-provider-c3os"
+    binary: "agent-provider-c3os"
 source:
   enabled: true
   name_template: '{{ .ProjectName }}-{{ .Tag }}-source'