Clean up some old artifacts.
Updated README.
Moved the task API to service.taskexecution project.
Refactored the old API project:

- moved most of the code to ols.common;
- moved some of the code to lib.swing.
Simplified the handling of OLS acquisition data:

- introduced an AcquisitionDataBuilder for creating AcquisitionData
  instances on the fly;
- introduced a generic OlsDataHelper for reading/writing OLS capture
  files;
- refactored most places where CapturedData was used to use the
  newly introduced AcquisitionDataBuilder.
Refactored the demo device:

- make use of the AcquisitionDataBuilder instead of CapturedData.