edit-jobset: make the "add a new input" button span the whole way

Dependencies

• [2] ZCO73ATU Add fontawesome as required by newer bootstrap
• [3] RQI3GRC6 Enable setting checkresponsible in the edit jobset form
• [4] OX6NYJDV Split viewing and editing a jobset
• [5] VJFLX7B6 Fix rendering of jobset inputs
• [6] 2G63HKCH Fix some wellformedness issues

Change contents

• replacement in src/root/edit-jobset.tt at line 54
  [3.2042]→[2.575:741](∅→∅)
  − <td colspan="4" style="text-align: center;"><button type="button" class="add-input btn btn-success"><i class="fas fa-plus"></i> Add a new input</button></td>
  [3.2042]

  [3.2216]
  + <td colspan="5" style="text-align: center;"><button type="button" class="add-input btn btn-success"><i class="fas fa-plus"></i> Add a new input</button></td>