* open header for custom kernel

* add core utils

* tidy core code

* tify header

* tidy include

* tidy namespace

* resolve conflit

* fix unittest and coverage

* remove platform using

* resolve conflict

* resolve conflict

* fix digamma namespace error

* fix xpu full kernel error

* fix xpu full kernel error

* polish details

* add place for lib storage

* move digamma to pten; test=develop

* fix mutable_data bugs; test=develop

* remove useless code; test=develop

* remove kernel compute; test=develop

* fix bug; test=develop