This patch saves the bank information in the DB, in a new table. It also
adds two new CLI commands, register/unregister, so enter the banking
information. (This should later be done internally).
It also adds new types alias for the DB transaction type and new
converters.
Input `transactions` method renamed to `parse`.
Issue #18
Adds a new abstract `Input` interface for the manager to use different
input handlers with the same methods. The Nordigen class and a new JSON
parser descend from it. The previous csv parser will also eventually.
New converter for list input also added.
Issue #19