BTCondition add invert option

[alijaya]

Problem statement

For now we need to use Inverter Decorator to invert the result of BTCondition, it's make the tree more cluttered.

Proposed solution

That would be great if BTCondition has invert variable that could change the SUCCESS into FAILURE and FAILURE into SUCCESS.

Alternatives

For now we need to use Inverter Decorator, but if it has built-in function for that, it would make it more readable.