Addition/deletion of centroids

Operations for additioin and deletion of centroids that use resizeable arrays are now tested and stable.

I have introduced new configuration parameters for DeSTIN:
* freqCoeff  - how fast estimated frequency of centroid is changing
* freqTreshold - if estimated frequency deteriorates below this treshold the centroid is removed
* addCoeff - a new centroid is added to a layer with probability addCoeff * absvar ^ 2

The commit includes:
* support for new parameters
* many bug fixes of centroid arrays operations
* more informations about quality for letters experiment
* merged Ted's refactorings and comments