Replace AbstractProject and AbstractBuild with Job and Run

[proski]

*  Replace AbstractProject and AbstractBuild with Job and Run
   
   This makes it possible to support pipelines. Pipelines don't use
   AbstractProject and AbstractBuild. Instead, they use WorkflowJob and
   WorkflowRun. The common ancestors are Job and Run.
   
   In some cases, Job doesn't provide the needed API. However, both
   AbstractProject and WorkflowJob implement ParameterizedJob interface,
   which provides the required functionality.

This is the commit from #69 that converts the remaining code to the types compatible with pipelines. It doesn't enable pipeline support, but it includes changes necessary to support pipelines.

The patch was authored by @rhencke and I'm not going to add my code to it, such as unit tests. I can add them separately.

[rhencke]

@proski Feel free to add your code as you wish, far as I'm concerned, if it helps. :)

[jakub-bochenski]

Thanks for the initial work @rhencke

@proski can you please double check my conflict resolution here?

[proski]

A fix is needed for a compile error, I've submitted a one-line fix: #114
Apart from that, the code is good. Checked that by diffing with the current pipeline-support~1
It's very good to have this PR merged, I'll be able to make bigger changes without being afraid of difficult merges ahead.