* Created TORCH_MODULE macro
Rewrote Linear
Rewrote Dropout and added default constructor to TORCH_MODULE macro
Turned TORCH_MODULE contens into a proper base class
Added some documentation
Got rid of the old Dropout module
Got rid of the old Embedding module
Got rid of the old BatchNorm module
Got rid of the old Conv module
Fixing optimizers
Rebase
Removed old RNN modules and the TORCH_ATTR macro
Removed temporary P:: namespace
Added cloning behavior to all modules
Got rid of some get() calls
self review nits
Remove noexcept from ModuleHolder methods that can throw
Remove spaces
Add missing override to reset() methods
Added examples to documentation in pimpl.h
* Post rebase fixes
