Settings: calendar selection

While it's quite simple to move event from one calendar to another on Harmattan, neither BlackBerry 10, nor Symbian allow this: calendar selection field is locked when you edit an existing event on BlackBerry 10 and it's locked on Symbian if event was synced with remote service at least once. Currently, Fahrplan adds journeys to default calendar but there might be a case when user wants to add journeys to non-default one. This change implements calendar selection in Settings. Fahrplan will fall back to default calendar if no calendar is set or selected calendar doesn't exist anymore.

There are few new strings, so translations were updated too. Please, check German translation for correctness.

@mzanetti, could you, please, update Ubuntu Touch port? There are two things to do:

1. Find out which calendar properties are responsible for marking calendar hidden, read only, etc. [Line 125 in src/fahrplan_calendar_manager.cpp](/leppa/fahrplan/blob/e404fc6a7a/src/fahrplan_calendar_manager.cpp#L126-L141) has more information on this.
2. Update Settings Page with calendar drop down list and selection code.