it was in the tests-folder, probably by accident?

Following @schoettl's suggestion to have better readability in the
IncidentDatabase

Updated and fixed test for maxSpawnNumberTotal

Max spawn number

This branch adds a maximum spawn number to the SourceAttributes.

Use case:

```
	 * This attribute can be used together with non-constant distributions. For
	 * example, consider an exponential distribution. The times of events are
	 * random. How to ensure, that exactly 10 elements are spawned? Solution:
	 * Set the {@link endTime} to 1e9 and this attribute to 10.
```

See merge request !4

Source spawn distribution

This branch gets rid of the old spawn algorithm und uses the new one.

By default, the new spawn algorithm works like the old one: constant inter-spawn times.

The new algorithm can be configured to use different spawn distributions, e.g.

```
      "sources" : [ {
        "id" : 1,
        "shape" : {
           ...
        },
        "spawnDelay" : -1.0, /* this one does not exist anymore */
        "interSpawnTimeDistribution" : "org.apache.commons.math3.distribution.ExponentialDistribution",
        "distributionParameters" : [ 1.4 ], /* mean for exponential distribution: 1.4 s */
        "spawnNumber" : 1,
        ...
```

The default distribution is: `org.vadere.state.scenario.ConstantDistribution`

There is an automatic migration from "not a release" to version 0.1 which drops the `spawnDelay` property.

See merge request !3

The new one passes all tests of the old one.

I searched for occurrences of Attributes or AttributesSource together
with Map/Set

suggestion by Jakob
c614a3ab
add21ddd0d0#note_16646

new specialized incident, requested by Jakob

The other one was bug: it tested the legacy spawn algorithm.

These lines were never executed because AttributesCar extends
AttributesAgent.

determineNumberOfSpawnsAndNextEvent did not always what it said.
I extracted the condition to a new method processNextEventIfItIsTime.