Improve error message anf description string
Merge pull request #56 from nbessi/fix_base_bank_only

Port of base_bank based on PCatinean work
[ADD] l10n_ch_dta ported to the new api
[ADD] 'Agile Bussiness Group' as contributor of porting to v8.0
[FIX] Delete duplicate and unitil code
[FIX] W0403(relative-import) pylint error
[FIX] add line on false postal number