* remove SliceCopied

* remove SliceCopied

* rename SliceShared to SliceLevels, SliceInLevel

* merge lod_tensor/details

* remove lod_start_pos_'s shared_ptr

* make lod-tensor a special tensor

* add clone to lod_tensor

* add lod tensor impl

* add lodtensor clone test

* init lod

* add equal

* merge LOD and its methods

* recover tensor and variable

* change thrust to host_vector

* add lodtensor

* add reshape of lod

* add details

* rename Elements/Levels

* size_t and vector reserve

* add details

* add const& std::shared_ptr

* add lod_tensor_impl.h

* remove a shared_ptr