aqbanking: 5.5.1 -> 5.6.10

Upstream changelog for version 5.5.1 through 5.6.10 is in German only
and also not very detailled, so here is a comparison from a GitHub
mirror I've found:

https://github.com/cstim/aqbanking/compare/5.5.1...e129e64472a2



I've also used a similar scheme to what I've been using for gwenhywfar,
so that we can soon unify all of the aqbanking & related libraries.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Cc: @cillianderoiste, @urkud