[FEATURE] SignalToNoiseEstimatorMedianRapid

- A SignalToNoise estimator based on median calculation but
  significantly faster than the SignalToNoiseEstimatorMedian
[TEST] add test for SignalToNoiseEstimatorMedianRapid
[FEATURE] PeakPickerMaxima

- maxima-searching PeakPicker based on PeakPickerHiRes
- this peak picker uses a cleaner interface and the new rapid signal to
  noise estimation
[FIX] performance improvement

- replace std::map with two doubles to keep track of current status of
  peak
[INTERNAL] move code to cpp file
[TEST] remove test to show numerically compatibility

- remove test to show numerically compatibility between the
  SignalToNoiseEstimatorMedian and rapid version
- the test took too long to execute, did not contribute significantly to
  unit testing
[FIX] switch to new Eigen spline

- use Eigen splines instead of gsl
[TEST] re-add old test files

- add new test files (after change by GSL removal)
[FIX] adopt tests for Eigen splines
[FEATURE] switch to Wm5 splines
[TEST] adopt tests to Wm5 splines
[TEST] add further tests
[TEST] Speedtest

fix speedcheck
Merge branch 'develop' into feature/PeakPickerSNPerformance_cr
[FEATURE] switch to CubicSpline2d
[FIX] fix spline derivative for cubic spline

fixed spline derivative for cubic spline
[TEST] adopt tests to cubic spline interpolation
[TEST] adapt and fix tests
[FIX] remove extra bracket

- some compilers (gcc > 4.6) try to honor the extra bracket and compute
  x*x explicitly, leading to suboptimal code.
- removing the bracket is clearer and leads to better code
Merge pull request #817 from hroest/fix/spline_derivative

[FIX] fix spline derivative for cubic spline