D18019: [Digital Clock] Add ability to set a custom date format string

[Chris Holland]

Zren added inline comments.

INLINE COMMENTS

> configAppearance.qml:145
> +                    'name': "custom"
>                  }
>              ]

Does this also need a `i18nc("custom date format", "Custom")` translation 
context?

REPOSITORY
  R120 Plasma Workspace

REVISION DETAIL
  https://phabricator.kde.org/D18019

To: Zren, #plasma, #vdg
Cc: rooty, plasma-devel, kvanton, jraleigh, GB_2, ragreen, Pitel, ZrenBot, 
lesliezhai, ali-mohamed, jensreuterberg, abetts, sebas, apol, mart