New file wizard

The new file wizards helps users to create a new file by
* setting up portfolios and accounts
* optionally adding investment instruments
  (for example securities from the DAX)

Signed-off-by: simpsus <bastian.kennel@gmail.com>
Improve new file wizard

Changes resulting from pull request comments:
* changed visibility
* closing intro page only if an editor was opened
* formatting
* skipping trailing spaces in suggest securities file
* prevent securitites from getting added twice
* disable table widgets to prevent selection