Allow defining additional characters for the password generator

See issue #3271 for a motivation of this feature.

This patch adds an additional text input to the advanced view of the password generator.  All characters of this input field (if not empty) will be added as another group to the password generator.  The characters from the excluded field have precedence over the characters from this new field, meaning any character added to both fields will *not* appear in any generated password.  As the
characters from this new field will be added as their own group to the password generator, checking the 'Include characters from every group' checkbox will
force at least character to be chosen from the new input field.

The `PasswordGenerator` class has also been changed so that the `isValid` method returns `true` if only characters from the new input field would be used.

There is a new, simple test that covers the new feature.  While the test only uses ASCII characters, any Unicode characters can be used with the new feature.

1 files changed, 1 insertions, 0 deletions

diff --git a/tests/TestPasswordGenerator.h b/tests/TestPasswordGenerator.h
index 56c4d65a1..454d16e06 100644
--- a/tests/TestPasswordGenerator.h
+++ b/tests/TestPasswordGenerator.h
@@ -26,6 +26,7 @@ class TestPasswordGenerator : public QObject
 
 private slots:
     void initTestCase();
+    void testAdditionalChars();
     void testCharClasses();
     void testLookalikeExclusion();
 };