l10n_lu account chart: add missing mappings between account chart and financial reports

Accounts 756, 758 and 759 should be the only one not mapped as 
the mapping is ambiguous, and child accounts should me mapped individually.
l10n_lu account chart: align account names with latest eCDF field list
[MERGE] l10n_lu: update account labels to match latest eCDF values + improve mapping with financial reports (bs, p&l), courtesy of Stéphane Bidoul (Acsone)