CASAS: fuel: Functions to get activity and feature by index
CASAS: fuel: Functions to get activity and feature by index

Functions are added to get activity label and feature string given
their indices. Those functions are used to represent learning
performance in a meaningful way.

Signed-off-by: Tinghui Wang <b242afeef4efadf7acab60ba9204ad943623eea5@wsu.edu>

TinghuiWang/pyActLearn