i18n: fix sign up strings

To avoid conflicting with existing strings in translations. Also improve localizability.

options/locale/locale_en-US.ini

@@ -408,8 +408,8 @@ remember_me = Remember this device
 remember_me.compromised = The login token is not valid anymore which may indicate a compromised account. Please check your account for unusual activities.
 forgot_password_title= Forgot password
 forgot_password = Forgot password?
-need_account = Need an account?
-sign_up_now = Register now.
+hint_register = Need an account? <a href="%s">Register now</a>.
+sign_up_button = Register now.
 sign_up_successful = Account was successfully created. Welcome!
 confirmation_mail_sent_prompt = A new confirmation email has been sent to <b>%s</b>. Please check your inbox within the next %s to complete the registration process. If the email is incorrect, you can log in, and request another confirmation email to be sent to a different address.
 must_change_password = Update your password

templates/user/auth/finalize_openid.tmpl

@@ -35,7 +35,7 @@
 					{{if .ShowRegistrationButton}}
 						<div class="inline field">
 							<label></label>
-							<a href="{{AppSubUrl}}/user/sign_up">{{ctx.Locale.Tr "auth.sign_up_now"}}</a>
+							<a href="{{AppSubUrl}}/user/sign_up">{{ctx.Locale.Tr "auth.sign_up_button"}}</a>
 						</div>
 					{{end}}
 					</form>

templates/user/auth/signin_inner.tmpl

@@ -57,8 +57,7 @@
 
 		{{if .ShowRegistrationButton}}
 			<div class="field">
-				<span>{{ctx.Locale.Tr "auth.need_account"}}</span>
-				<a href="{{AppSubUrl}}/user/sign_up">{{ctx.Locale.Tr "auth.sign_up_now"}}</a>
+				{{ctx.Locale.Tr "auth.hint_register" (printf "%s/user/sign_up" AppSubUrl)}}
 			</div>
 		{{end}}
 	</div>