make connectivity and quota views translatable (#2694)

* add missing stock strings for connectivity and quota

* reword quota error

* use 'Incoming/Outgoing Messages' instead of 'Inbox/Outbox'

* just say 'Not supported by your provider.' if quota cannot be read.

- the context is already given by the headline
  'Storage on domain.org'
- the string is short and does not disturb much
  (it is a very common error)
- the string does not mention 'quota' as such,
  which will be hard to translate ('Kontingentsinformationen') -
  even if ppl as we know about the Quota extensions an such things.

there was also the idea to hide the whole section,
however, that is confusing in a multi-device-usage
when things are sometimes shown and sometimes not.

deltachat-ffi/deltachat.h

@@ -5900,6 +5900,70 @@ void dc_event_unref(dc_event_t* event);
 /// `%1$s` will be replaced by human-readable date and time.
 #define DC_STR_DOWNLOAD_AVAILABILITY      100
 
+/// "Incoming Messages"
+///
+/// Used as a headline in the connectivity view.
+#define DC_STR_INCOMING_MESSAGES          103
+
+/// "Outgoing Messages"
+///
+/// Used as a headline in the connectivity view.
+#define DC_STR_OUTGOING_MESSAGES          104
+
+/// "Storage on %1$s"
+///
+/// Used as a headline in the connectivity view.
+///
+/// `%1$s` will be replaced by the domain of the configured email-address.
+#define DC_STR_STORAGE_ON_DOMAIN          105
+
+/// "One moment…"
+///
+/// Used in the connectivity view when some information are not yet there.
+#define DC_STR_ONE_MOMENT                 106
+
+/// "Connected"
+///
+/// Used as status in the connectivity view.
+#define DC_STR_CONNECTED                  107
+
+/// "Connecting…"
+///
+/// Used as status in the connectivity view.
+#define DC_STR_CONNTECTING                108
+
+/// "Updating…"
+///
+/// Used as status in the connectivity view.
+#define DC_STR_UPDATING                   109
+
+/// "Sending…"
+///
+/// Used as status in the connectivity view.
+#define DC_STR_SENDING                    110
+
+/// "Your last message was sent successfully."
+///
+/// Used as status in the connectivity view.
+#define DC_STR_LAST_MSG_SENT_SUCCESSFULLY 111
+
+/// "Error: %1$s"
+///
+/// Used as status in the connectivity view.
+///
+/// `%1$s` will be replaced by a possibly more detailed, typically english, error description.
+#define DC_STR_ERROR                      112
+
+/// "Not supported by your provider."
+///
+/// Used in the connectivity view.
+#define DC_STR_NOT_SUPPORTED_BY_PROVIDER  113
+
+/// "Messages"
+///
+/// Used as a subtitle in quota context; can be plural always.
+#define DC_STR_MESSAGES                   114
+
 /**
  * @}
  */