Emable overriding the email template.

Dependencies

• [2] LDICTHWY Use Template::Toolkit to generate email messages
• [3] RPTSGIRC Eliminate duplicate getPreviousBuild functions
• [4] QDJRQIFF If multiple dependent builds fail, send a single email
• [5] E6SL7QRU Omit the system type if it's part of the job name
• [*] 5EQYVRWE Add a plugin mechanism

Change contents

• replacement in src/lib/Hydra/Plugin/EmailNotification.pm at line 17
  [3.488]→[2.450:472](∅→∅)
  − my $template = <<EOF;
  [3.39]

  [2.472]
  + my $template = $ENV{'HYDRA_EMAIL_TEMPLATE'} || <<EOF;