A bit of an optimizer overhaul, added an improved factory, list_optimizers, class helper and add info classes with descriptions, arg configs

Author: rwightman

tests/test_optim.py

@@ -17,4 +17,5 @@
 from .rmsprop_tf import RMSpropTF
 from .sgdp import SGDP
 
-from .optim_factory import create_optimizer, create_optimizer_v2, optimizer_kwargs
+from ._optim_factory import list_optimizers, get_optimizer_class, create_optimizer_v2, \
+    create_optimizer, optimizer_kwargs, OptimInfo, OptimizerRegistry