d-t-m and annotator update for fixing PDF

 * Updated d-t-m to 654e58a2 (observer-5 branch)
 * This version of d-t-m ships with pdf-text-mapper, which previously
   lived in Annotator's PDF plugin.
 * Followed d-t-m packaging change: add the new TextMapperCore script
 * Update Annotator's PDF plugin to 0ac95fc0 (observer-6 branch)

This fixes the broken PDF support on the observer branch.
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