Install Abiword

Summary:
Issues with Abiword are solved with recent versions.

Tested under Etherpad recent code (1fce593779) on Node v9.11.2.

Ref T1419

Test Plan: Rebuild image, check export still works fine

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1419

Differential Revision: http://devcentral.nasqueron.org/D1729