Merge branch 'hotfix/1.7.3'
Support external images in PDF image #1468
Process common attributes in chhead in XHTML #1469
Fix PDF colwith percentage unit bug #1477
Correct path in error message #1475
Fix msgblock output in PDF #1472
Fix index entry bug in PDF using XEP #1423
Merge pull request #1480 from keberlein/develop

Correcting values for the @relcolwidth attribute
Update testsuite
Merge pull request #1481 from keberlein/develop

Adding CSS file for the XHTML-based formats of the DITA-OT documentation
Refactor Job object to be file centric

Change file list based job configuration to store properties into file
info objects.
Refactor troff plug-in to separate base plain text output
Update doc build to use CSS, include task labels
Merge branch 'develop' of github.com:dita-ot/dita-ot into develop
Merge branch 'hotfix/1.7.4'
Merge branch 'hotfix/1.7.4' into develop
Fix distribution build
Preserve language for default revision flags #1484
New doc topic on changes to content #1465
Merge pull request #1485 from keberlein/develop

Documentation updates