Add Keep email private (see issue #571). (#571)

- Add site-wide option DEFAULT_KEEP_EMAIL_PRIVATE.
- Add the new option to the install and admin/config pages.
- Add the new option to app.ini in the service section.
- Add the new option to the settings struct.
- Add English text strings to i18n.
- Add field KeepEmailPrivate to user struct.
- Add field KeepEmailPrivate to user form.
- Add option to UI.
- Add using noreply email address if user has "Keep Email Private".
An email address <LowerName>@<NO_REPLY_ADDRESS> is now used in commit
messages (and hopefully all other git log relevant places). The
change relies on the fact that git commands should use
user.NetGitSig().
- Add hiding of email address in UI, if user has set "Keep Email Private".
- Add condition to show email address only on explore/users and user
pages, if user has not set "Keep Email Private".
- Add noreply email in API if set "Keep Email Private".
- Add a new service setting NO_REPLY_ADDRESS. The value of this
setting is used as the domain part for the user's email address in
git log, iff he decides to keep his email address private.
If the user decides to keep his email address private and this
option is not set 'noreply.example.org' is used, which no MTA
should send email to.

Add NO_REPLY_ADDRESS to conf/app.ini.

modules/auth/user_form.go

@@ -38,12 +38,14 @@ type InstallForm struct {
 	RegisterConfirm bool
 	MailNotify      bool
 
-	OfflineMode           bool
-	DisableGravatar       bool
-	EnableFederatedAvatar bool
-	DisableRegistration   bool
-	EnableCaptcha         bool
-	RequireSignInView     bool
+	OfflineMode             bool
+	DisableGravatar         bool
+	EnableFederatedAvatar   bool
+	DisableRegistration     bool
+	EnableCaptcha           bool
+	RequireSignInView       bool
+	DefaultKeepEmailPrivate bool
+	NoReplyAddress          string
 
 	AdminName          string `binding:"OmitEmpty;AlphaDashDot;MaxSize(30)" locale:"install.admin_name"`
 	AdminPasswd        string `binding:"OmitEmpty;MaxSize(255)" locale:"install.admin_password"`
@@ -97,11 +99,12 @@ func (f *SignInForm) Validate(ctx *macaron.Context, errs binding.Errors) binding
 
 // UpdateProfileForm form for updating profile
 type UpdateProfileForm struct {
-	Name     string `binding:"OmitEmpty;MaxSize(35)"`
-	FullName string `binding:"MaxSize(100)"`
-	Email    string `binding:"Required;Email;MaxSize(254)"`
-	Website  string `binding:"Url;MaxSize(100)"`
-	Location string `binding:"MaxSize(50)"`
+	Name             string `binding:"OmitEmpty;MaxSize(35)"`
+	FullName         string `binding:"MaxSize(100)"`
+	Email            string `binding:"Required;Email;MaxSize(254)"`
+	KeepEmailPrivate bool
+	Website          string `binding:"Url;MaxSize(100)"`
+	Location         string `binding:"MaxSize(50)"`
 }
 
 // Validate valideates the fields