Split the tests in performance and unit tests

* New source folders src-perftest and src-unittest
* Buildziele
    Performance Test – Debug, Enhanced Debug, Release
    Unit Test – Debug, Enhanced Debug, Release
* Adapt gitignore to exclude the new build folders.
* The CMake configuration is not yet adapted.
Add todo comments about sampling and the real C++11 random header.
CategoricalDistribution: Fix signature of assignment with
initializer_list.
Reformat DirichletDistribution.hpp.
DirichletProcessNode: Extract the computation of the distribution from
init_sampling and sampling

* This makes both sampling functions clearer and better testable.
  A test can check the sampled value and the distribution.
Fix the name of the Dirichlet parameter node in InfiniteBagTest.

* The naming has changed a couple of commits before, but I forgot
  to update this test.
Move Test.hpp into src-lib.

* This is necessary, because both, the performance tests and the unit
  tests should use this header.
* The new location is not the right place though. A new source folder
  would be necessary, which contains files that are shared by both
  kinds of tests.
Add ListNumberGenerator.

* This is a random number engine that takes its numbers from a user
  provided list.
* This engine is necessary for full control in tests. The unit tests
  will use it.
Improve the DirichletProcessTest

* Test the sampling distributions (prior and posterior).
* Use the new number generator to get predictable results.
* Refactor the result checking to get easily understandable and
  reusable actions.
Rename the performance test – release target to perftest-release.

* I could not get it run in Texttest with the spaces in the folder
  name.