core+gui+cli: network-fee invalidation, will-tree fixes, i18n refresh

- #64: the on-chain invalidation now pays the current network fee through a
  configurable fee-policy setting (default eta:2); baltx_fees is only the
  offline fallback. The change output is dust-guarded: coins are appended until
  the change clears the wallet dust threshold.
- #65: a will item whose father is missing/stale is handled defensively in
  check_invalidated and discarded by add_willtree instead of raising KeyError.
- #66: children are stored as a list (dict accepted for older data/tests).
- Refresh the translation catalogs and fix stale source line references.
- New tests for the invalidation fee policy, the dust guard and the father
  link handling.

bal/gui/qt/dialogs.py

@@ -747,6 +747,7 @@ class BalBuildWillDialog(BalDialog):
                     self.bal_window.willitems,
                     default_value=self.bal_window.date_to_check,
                 ),
+                fee_policy_descriptor=self.bal_window.bal_plugin.INVALIDATION_FEE_POLICY.get(),
             )
             if tx:
                 _logger.debug(
@@ -842,6 +843,7 @@ class BalBuildWillDialog(BalDialog):
                     self.bal_window.willitems,
                     default_value=self.bal_window.date_to_check,
                 ),
+                fee_policy_descriptor=self.bal_window.bal_plugin.INVALIDATION_FEE_POLICY.get(),
             )
         except NoHeirsException:
             _logger.debug("no heirs")