removed disc_routines
use of the add_to_routines private function
solve_function_mode replaces solve_use_disc

The options are ['explicit','disc','vectorized']
update for evaluating vectorized expressions
comment for disc functions written after function
New method for transforming array of anonymous into one anonymous
More flexible printing of derivatives
improved costly memoization
utility for creating function handles for m-files
making use of the new func2fhandle