7.8.3-1.9.0

This is an updated version for Bonita 7.8.

No major change in the features used.
Main update is to use contract wizard to define the contract on the step on the user task. This is done to anticipate future tooling of Bonita 7.9.

An attempt is done to update the build tooling (for exercises DocBook files) to a more standard and up to date solution.