[PATCH] HouseNumberTaggingTool: increment house number suffixes (1a, 1b, ... or 1/1, 1/2, ...)

[Till_btn]

When mapping addresses like 5, 5a, 5b, 6 the suffix has to be typed by hand
every time. The attached patch adds:

• New option "Increment suffix" next to "Increment number": 1 -> 1a -> 1b, also works for 1-a, 1/A and 1/1 -> 1/2. The selected mode is saved like the other settings
• New shortcut Shift+K opens the dialog and switches between number and suffix, e.g. 5 -> 5a or 5c -> 6.
• incrementHouseNumber() now also accepts numbers like 1/1 or 1-a (previously returned null)