Free choice

[vldtecno]

Implement free choice nets.
Multiple choice scenario: more than one transition is active at the same time because of a common place and after one of them fires the others can no longer fire.
The decision of which to be fired should be random. Each transition should have an equal probability of being fired.
(At the moment it depends on the order on the insertion order of transitions in the vector, so it is not random. )

[vldtecno]

Implemented this feature in the dev branch. Merged to the v_1_1_x branch also.

Implementation details:

• on execution iterate through all transitions
• check which can be fired
• create a vector with pointers to the transitions that can be fired.
• randomize this vector.
• iterate through the randomized vector and execute in order each transition.

[vldtecno]

A Unit test was also added to the black box tests.
dev: 5d0e155
v_1_1_x: b578afb