0.1.7

• Fix EÜR schema rejection: USt_StFrei now emits before
  USt_Vereinnahmt_Unentgeltl and USt_Erstattet_Verrechnet after
  it, as the XSD demands. Filings with reverse-charge income
  (rate=0 rows) were rejected with EC(1000) before this.
• Example project covers rate=0 income; e2e tests assert element
  ordering.
• fetch: ERiC 43.4.6.0 (43.3.2.0 was pulled from ELSTER's server,
  breaking fresh installs and CI).