Finite Difference test

[llaniewski]

Adding:

1. testing of Adjoint gradient against Finite Difference:

<FDTest order="2">
<Adjoint>
<Solve Iterations="100"/>
</Adjoint>
</FDTest>

1. GenericOptimizer handler class, for all handlers evaluating solutions for changed parameters (in future Threshold handler will be also reimplemented as GenericOptimizer)
2. mechanism for skipping adjoint when gradient is not needed (for instance when Optimize uses a non-gradient algorithm.
3. dumping of time dependent settings to a csv file (a simple dump, more for debugging purposes): <DumpSettings\>