app: Allow to list account names in the command line
app: Guess by substring match for an account
app: When importing lookup account from filename
tests: moved into designated place
models: specify a better table name.

When introspecting tables and their transactions, that'll make things
easier, since the table name does not have to be quoted anymore.
models: Use the account number as identifier
models: Use pycountry for currency lookup
models: use an institute as a container for accounts
models: Don't guesswork new instances.

There is too much information we need. Guessing will just not work at
the moment.
tests: coverage need to use the same paths