Refactor stream master constructor

Created by: michele-brambilla

Description of work

With this PR the StreamMaster delegates a new object (the StreamerFactory) to construct the Streamers. Advantages:

• StreamMaster is no more a template class
• the AbstractStreamerFactory let us add stub Streamers that can be used to test the StreamMaster
• the StreamerBase class implements all the public methods of the Streamer but pollAndProcess. This makes easier test the Streamer.

The StreamMaster constructor has changed. Some informations are now collected from MainOpt rather than constructor arguments.

The Streamer doesn't handle the sources list: a new object (the SourcesHandler) is in charge of doing that.

Acceptance Criteria

• The StreamMaster can be constructed using different types of Streamer

Unit Tests

• Added tests for the StreamerFactory
• Added tests for the StreamMaster
• Added tests for the SourceHandler

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Code Review (To be filled in by the reviewer only)

• Is the code of an acceptable quality?
• Do the changes function as described and is it robust?

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