fix(core): Require current password on password change (#285)

Increase security by requiring the current password when changing the
password. This increases the security for cases such as XSS, or just a
forgotten browser window left open.

Fixes #4140

UI/PreferencesUI/English.lproj/Localizable.strings

@@ -238,6 +238,7 @@
 "Additional Parameters" = "Additional Parameters";
 
 /* password */
+"Current password" = "Current password";
 "New password" = "New password";
 "Confirmation" = "Confirmation";
 "Change" = "Change";

UI/PreferencesUI/German.lproj/Localizable.strings

@@ -233,6 +233,7 @@
 "Additional Parameters" = "Zusätzliche Einstellungen";
 
 /* password */
+"Current password" = "Aktuelles Passwort";
 "New password" = "Neues Passwort";
 "Confirmation" = "Bestätigung";
 "Change" = "Ändern";