Change App-Icon to ownCloud Notes Logo

[stefan-niedermann]

The App-Icon should be identical to the ownCloud Notes Logo.
@jancborchardt - would you like to take this one?

[jancborchardt]

Yeah, can do. Also need to fix that for the Notes web app favicon anyway. cc @Henni @Raydiation @owncloud/designers

[stefan-niedermann]

@jancborchardt If you could answer my questions on owncloud/android@2afd2d6 i would be able to generate the icon myself :)

[stefan-niedermann]

Fixed by 7460d38.