This addresses the issue of len() for FrSimData.data member

This closes #71 (closed) by converting the FrSimData::data to be of Container instead of SearchContainer This closes #61 (closed) by adding unit test verifying correct operation This corrects a subtle bug in the CI script where the local ldas-tools debian packages where not installed. The system available packages were installed instead which lead to random SEGFAULTs in several unit tests because data structures had changed in size.