Add the email-templates endpoints
https://auth0.com/docs/api/management/v2#!/Email_Templates/get_email_templates_by_templateName

Things open to discuss:

• The use of constants. They can be provided by us or not. The problem is that the endpoint only accepts a given set of values. We can also use an Enum class instead. I've added this:

 public static final String TEMPLATE_VERIFY_EMAIL = "verify_email";
 public static final String TEMPLATE_RESET_EMAIL = "reset_email";
 public static final String TEMPLATE_WELCOME_EMAIL = "welcome_email";
 public static final String TEMPLATE_BLOCKED_ACCOUNT = "blocked_account";
 public static final String TEMPLATE_STOLEN_CREDENTIALS = "stolen_credentials";
 public static final String TEMPLATE_ENROLLMENT_EMAIL = "enrollment_email";
 public static final String TEMPLATE_CHANGE_PASSWORD = "change_password";
 public static final String TEMPLATE_PASSWORD_RESET = "password_reset";
 public static final String TEMPLATE_MFA_OOB_CODE = "mfa_oob_code";

• Method visibility (scope) of the values that can't be changed once set. The template name ("template" property in the object) can't be changed once set. Since the same Template class is used on the create and update methods, does it make sense to have 2 constructors, one that accepts all the values required for creation (4 or 5 values, can be seen on the corresponding test) and one without any values so people uses the first one for creation and the other for existing templates update?

• The methods were added following a REST pattern of parameters doAction(id, data). In this particular case, the "Template Id" is the template's name, used on the path. And it must match the one defined in data.template, or that property should be ignored at all when updating templates. WDYT?