Peter M. Groen / openbr

Change default label name from Subjet to Label (since label is a more general
term).
Use different default variable names for classification (label), regression
(regressor/regressand), and clustering (ClusterID)
Update some (far from all) transforms to accept arguments specifying their
input/output variables.
Update eval classification to optionally take target variable names as
arguments

Remove global label/subject lookup table
Consistently use "Subject" rather than "Label", subject is assumed to be
convertable to QString. When desirable, map discrete subject values to ints.

For classifiers such as svm that require numeric labels, generate a string->int
mapping for the training data, and store it (local to the transform).

Utility functions for collecting all values of a given property (on a template
list), and mapping discrete property values to 0-based integers

Some outstanding issues include use of label/subject in matrix output

Remove subject/label methods from the API, replace some methods with general
methods taking a property name as an argument.

This breaks quite a few things