added application of reference data points filters for ICPSequence objects

see issue #56.

Note that applying this change requires to go through the icp.yaml (and the like) files of a lot of existing setups (as in ethzasl_icp_mapping/ethzasl_icp_mapper/launch) and removing the reference data points filters. Otherwise I suppose that all this stuff will not work any more once the reference filters are active.