Updating plugin.go to allow versions

This change is it allow all possible versions in all plugins within update.jenkins.io, this is linked to issue:https://github.com/jenkinsci/kubernetes-operator/issues/144

pkg/controller/jenkins/plugins/plugin.go

@@ -21,7 +21,7 @@ func (p Plugin) String() string {
 
 var (
 	namePattern    = regexp.MustCompile(`(?i)^[0-9a-z-_]+$`)
-	versionPattern = regexp.MustCompile(`^[0-9\\.-]+$`)
+	versionPattern = regexp.MustCompile(`^[0-9\\.-]+(\..+)?$`)
 )
 
 // New creates plugin from string, for example "name-of-plugin:0.0.1"