Implement grid search for random forest parameters

[bburlacu]

This ticket is identical to #2234, only for random forests. Grid search should support searching for any combination of n, m, r parameters where:

• n is the number of trees in the forest
• m is the ratio of features that will be used in the construction of individual trees (0<m<=1)
• r is the ratio of the training set that will be used in the construction of individual trees (0<r<=1)

[bburlacu]

r11315: Added RandomForestUtil class implementing fold generation, cross-validation and grid search. Overloaded CreateRegressionModel method to accept a user-specified data partition.

[bburlacu]

r11317: Forgot to commit changes to project file.

[bburlacu]

r11337: Refactored SVM grid search, added support for symbolic classification.

[mkommend]

r11343: Corrected newly introduced bug in RandomForestModel and reorganized RandomForestUtil.

[mkommend]

Review comments:

• every call to createRFModel allocates a double[,] that holds the data => try to reuse the generated data objects
• adapt the method names and signatures to the ones in the SVMUtil class
• remove SVM related methods and objects from the scripts
• include a demo problem data in the script, so that it can be started directly
• the scripts should also work with problems and not only with problem data objects
• provide some kind of progress indication (e.g. printed dots, number of calculated combinations, ...)
• elapsed time has no unit displayed
• attach the scripts to the start page

[bburlacu]

r11362: Addressed part of the comments above:

• Methods are similar to the ones from SupportVectorMachineUtil
• Cleaned up sample scripts
• Elapsed time is shown in seconds
• Included demo problem
• Added stratified crossvalidation (shuffling is turned off by default)
• Added different GridSearch methods with/without crossvalidation.
• Fixed bug in fold generation when the number of folds is larger than the number of values

[bburlacu]

Sample script for Random Forest grid search (classification)

[bburlacu]

Sample script for Random Forest grid search (regression)

[bburlacu]

r11426: Fixed thread synchronisation bug. Removed unused variables in GridSearch methods.

[bburlacu]

r11443: Made random forest parameters serializable (by deriving from ParameterCollection).

[bburlacu]

r11445: Fixed cloning and storable constructor access levels

[bburlacu]

r11446: Added random forest grid search scripts to the HeuristicLab start page.

[bburlacu]

r11448: Added script to the startpage (forgot to commit changes to StartPage.cs).

[mkommend]

r11901: Merged r11315, r11317, r11338, r11343, r11362, r11426, r11443, r11445, r11446, r11448 into stable.