Create a filter stream

[ArnaudBuchholz]

Part of EPIC #155

As a developer, I want a stream-capable filter to select records from an input stream based on the a function

Acceptance criteria:

• The stream is created with a filter function as parameter: the filter function accepts one parameter
• The function is called for every write: if the result is true, the buffer is transmitted to the read, otherwise the buffer is dropped
• As a first implementation, the stream might be a pass-through stream (one in => zero or one out). If needed (to avoid bottlenecks), the stream may evolve to a buffered one