Pipelining of arbitrary filters

[codeling]

As a user, I want to be able to chain image processing filters in open_iA one after another and execute them all at once.

• There should be a nice interface (e.g. drag and drop as in PorosityAnalyzer module) to defines pipelines. Maybe this could work similar to existing data flow design solutions.
• The user should be able to store/load a pipeline.
• The user should be able to run defined pipelines on multiple files via the batch mode.
• Ideally, the pipeline should be itself be accessible as a filter, so that it e.g. can be sampled (see https://github.com/3dct/open_iA/issues/30)