Support for createNamespace (#1226)

- createNamespace is a new attribute that can be added to helmDefaults
  or an individual release to enforce the creation of a release namespace
  during sync if the namespace does not exist. This leverages helm's
  (3.2+) --create-namespace flag for the install/upgrade command. If
  running helm < 3.2, the createNamespace attribute has no effect.

Resolves #891
Resolves #1140

pkg/app/app_test.go

@@ -2168,6 +2168,14 @@ func (helm *mockHelmExec) IsHelm3() bool {
 	return false
 }
 
+func (helm *mockHelmExec) GetVersion() helmexec.Version {
+	return helmexec.Version{}
+}
+
+func (helm *mockHelmExec) IsVersionAtLeast(major int, minor int) bool {
+	return false
+}
+
 func TestTemplate_SingleStateFile(t *testing.T) {
 	files := map[string]string{
 		"/path/to/helmfile.yaml": `

pkg/app/mocks_test.go

@@ -82,3 +82,13 @@ func (helm *noCallHelmExec) IsHelm3() bool {
 	helm.doPanic()
 	return false
 }
+
+func (helm *noCallHelmExec) GetVersion() helmexec.Version {
+	helm.doPanic()
+	return helmexec.Version{}
+}
+
+func (helm *noCallHelmExec) IsVersionAtLeast(major int, minor int) bool {
+	helm.doPanic()
+	return false
+}