- Added 'ignore-missing' attribute to <term>, <match> and <set> tags to allow fine-grained user control of template generation in cases where <auto-prefix-list> tags are involved.
  Default behavior is conservative and aims to accept less or nothing, rather than more or all, when <auto-prefix-list> yields no results. This new attribute allows users to relax
  this a bit on several levels, allowing things that would normally be removed/denied.

- Added docs for 'ignore-missing' attribute.