* use line comments instead of multiline comments for license header

* update more

* update new files

* more header updates

* style

*  zero dimension tensor elimination init

* more ops + refactor + tests

* revert pattern.cpp

* add internal zero-length test

* address Scott's feedback

* fix comp errors

* proper static init

* get rid of unique-ptr

* refactor hashmap into virtual get_default_values on op classes

* fix formatting