Add default board on first use [$10 awarded]

[juliusknorr]

from #12:

• There should be one board called »Personal« by default from the beginning. Just like in the Calendar app with the first calendar, and for Contacts too with the default address book.
• There should be default stacks in the first board for sure, and ideally also in every one created: To do, Doing, Done

This might be a good starter issue to get a bit into the php code part. So if anyone wants to give it a try, here is how the implementation should basically look like:

• Implement a class OCA\Deck\Service\DefaultBoardService, methods could be checkFirstRun and createDefaultBoard
• checkFirstRun(): Add a user config value like 'firstrun' to check if the default board has already been created for the current user
• createDefaultBoard(): Create the board, stacks and cards that should appear by default
• check and call createDefaultBoard in PageController::index()

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The $10 bounty on this issue has been claimed at Bountysource.

[juliusknorr]

@artemanufrij Are you still up for this?