Depend on version 1.8 of the pipeline + latest dtbook-to-odt

- jodconverter not required anymore
- odt-utils still needs to be included because it is not in
  pipeline-assembly 1.8 yet
- p:import dtbook-to-odt/library.xpl

also:
- use pax-exam-helper for testing
- use x:script feature of xprocspec
Fixup ee3b026ac7eb9a0f1c2cc804585e3f9fb8fc9050

delete unused file
Move dependencyManagement to parent pom

see also sbsdev/maven-parents#1
Merge pull request #2 from sbsdev/pipeline_1.8

Depend on version 1.8 of the pipeline