8.0 import parsers

- Add framework to allow for easy conversion of 7.0 and previous style bank statement import parsers.
- As an example provide a (fully functional) convertion of the camt parser.

TODO: add more of the 7.0 functionality.

REMARK: settings have been removed here, as all the settings really apply to reconciliation, not to import.
Please extract this to README.rst file.