Include the replacement CCF gate in a corresponding basic event.

Now basic events are aware if they are in a CCF group or not. Currently,
basic events do not know which CCF group they are in, but they have only
replacement gate for analysis.
Make fault trees gather information about basic events of CCF groups.

Fault trees provide CCF basic events that are in their structure.
CCF generated basic events are included in general directories, assuming
that CCF analysis is the default behavior.
Implement analysis of Beta factor CCF.
closes #95
Add Beta Factor CCF benchmark test based on simple Three Train system.

This benchmark is not validated and needs more analysis to actually
become a benchmark.