TR0 change; futrig adjustments to align output with trigsimp

In all expressions, now, futrig gives an expression that is shorter
(in terms of str length) than trigsimp.
add docstring to trigsimp about compare, fu and futrig
wip
Merge branch 'fu' of github.com:smichr/sympy into fu
replace old trigsimp code with call to futrig

- also, trigsimp will always operate in a deep fashion so that
  keyword is now ignored
- there is no more caching of the results
- tests related to assumptions were removed since the patterns that
  were being tested were removed and those assumptions are part of
  the new fu-like transforms.