Simplify cut set gathering from an indexed fault tree.
Correct a coding standards link in readme file.
Change basic and house events to reflect their use.

Now house events are described by their states only and no probabilities
provided because they should not appear in minimal cut sets.
Separate basic events from house events in an original fault tree.

A separate container is provided for basic and house events in a fault tree.
This containers should make easier the indexation process and house event
state determination.
Introduce original module detection after pre-processing.
Separate complex XOR and ATLEAST gate unrolling from pre-processing.

This is needed for original module detection because unrolling complex
gates creates new gates that are not in original trees.
Fix a typo bug in unrolling complex gates and rename joining function.
Gather parents of indexed gates for future use.
Add experimental inputs for module detection and unity top special case.
Move cut set generation and minimization to simple gate pointers with
modules.
Introduce initial use of modules in fault tree analysis.
Detect limit order earlier upon module min cut set joining to the main
minimal cut sets.
Add a test for multiple parent negative gate bug #90.
Change gate unrolling strategy.
Fixes #90

Gates are unrolled sequentially without traversing the fault tree. The
parent information is used if gates are negative.
Rename the multiple parent negative gate test.
Create new modules by joining a non-module gate's children that satisfy
modularity.
Use indexed gate shared pointers.
Introduce special treatment of UNITY case of a top gate.
Add treatment for corner cases of UNITY.

The tree negative gates are preprocessed before any analysis.
Only positive gates are left.
Add UNITY treatment in uncertainty analysis.