feat(refacto): move everything in internal package

This allows to install katenary with `go install` and to clean up the
project folder.

internal/generator/labels/labelstructs/mapenv_test.go

@@ -0,0 +1,11 @@
+package labelstructs
+
+import "testing"
+
+func TestConfigMapLabel(t *testing.T) {
+	ts := "foo: bar"
+	tc, _ := MapEnvFrom(ts)
+	if len(tc) != 1 {
+		t.Errorf("Expected ConfigMapFile to have 1 item, got %d", len(tc))
+	}
+}