Introduce SimpleGate to represent pre-processed fault tree.
Replace IndexedGate by SimpleGate for core fault tree analysis.
Recover 200 event tests and fix minor bugs.
Simplify fault tree analysis class.

Time recordings for all the core analysis is performed. The detailed
performance should be gotten from the logging system. This means only
total time is reported in the output.

The fault tree analysis class is simplified to reduce variables and one
function on index assignment.
Introduce performance logging in indexed fault tree.

Performance logging is given for the parts to do expansion and mcs
generation.
Code cleanup. Redundant headers are removed.
Cleanup typedefs.
Merge branch 'develop' into coverity-scan