minor, extradite sigma/softmax routines to maths.[ch]

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, migrate dbn-test tool to using maths.h generics

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, major, rename dbn-test to rbm(1)

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'tool/rbm'

* tool/rbm:
  chore, major, rename dbn-test to rbm(1)
  minor, migrate dbn-test tool to using maths.h generics
  minor, extradite sigma/softmax routines to maths.[ch]