Improve validate output

The output is now much more condensed:
Validating all files
  Trailing or unnessary whitespaces found:
   glossary/glossary-terms.xml lines: 40, 1004, 2152
   user-guide/section_swift_cli_howto.xml lines: 2
   user-guide/section_dashboard_manage_volumes.xml lines: 20
   common/section_about-object-storage.xml lines: 4, 5
   common/tables/swift-container-server-container-updater.xml: lines 46

Change-Id: I501ba19360616688cf7e3f42636382dd426c83ce
Merge "Improve validate output"