Dialog: make cancel timeout configurable

[nephros]

• Dialog: make timeout configurable
• Dialog: use non-deprecated import
• Dialog: allow any orientation
• Dialog: Fix a warning

Contributes-To: #480

[Olf0]

LGTM

[Olf0]

@nephros, when trying to translate string #111 at Transifex, it appears to me that a "when rebooting" is missing in the original source string to make sense, correct?

Maybe we can even drop the lengthy "for the first time" and simply replace it with "when rebooting"?

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It also looks as if Transifex's string #121 (original source string here) then needs to be adapted accordingly, too: Both, to the recent changes of string #111 and the resolution of its issue addressed here.

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Less, but still slightly problematic appears to be string #46 at Transifex when comparing it to my draft of its de translation there (original source string here). It is not a brand new string, but when reviewing it now, it seems to provide too little information.

• Maybe I am simply lacking context, i.e. it all makes sense when looking at it in Patchmanager?
• There might be other translatable strings for handling the backup list, which need to be reviewed and enhanced in a similar manner.

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Edit: Transferred (in)to issue #504.