seealso added for functions from other packages
normalisation options added to confusion matrix
bugfix
normalise_over included as a seperate function
normalise_over implemented with higher level functions
relevel_by allows re-levelling by multiple vectors
var_groups spike added
More thought given to data hierarchy.

At the moment a frame can either be a training of testing frame, but not both.

fit_model => train
apply_model => test
code re-formatted
utils for testing frame added