* 1.Fix api sum:(1) input->sum; (2)dim->axis; (3)keep_dim->keepdim.

* 2. fix bug when len(axis) == len(x.shape). 

* expose and unify the Tensor concepts to the user

* expose tensor to user

* add copy place for Tensor

* add copy place for Tensor

* add note

* add macro PADDLE_WITH_CUDA

* remove RUN_TYPE=DIST

* fix some error

* Directory migration, test=develop

* Change imperative from paddle init to paddle framework, test=develop

* Fixed jit bug, test=develop

* default static mode, test=develop

* fixed format and create parameter belongs to framework, test=develop

* Fixed import package, test=develop

* fix __init__ format, test=develop

* fixed alias problem

* fixed paddle.enable_imperative problems, test=develop

* Add unittest

* delete install_check comment

* Fixed unittest timeout

* fixed unittest error

* move Program default_xx_program to static package

* optimize unittest method

* fixed framework __init__ format

* fixed jit path

* delete alias

* move jit to paddle

* Fixed unittest format

* fixed paddle.default_main_program

* Fixed save load API in paddle __init__.py

* fixed ci paddle.imperative.to_variable

* Move complex into dir incubate, test=develop

* Fix imports, test=develop

* Fix docs, test=develop

* Forbid import functions from paddle.incubate directly, test=develop

* add trace op, test=develop

* Optimized the implementation of trace op, test=develop

* fix a bug of include in trace_op.h, test=develop

* move trace API from creation to math, test=develop

* modified en doc. test=develop

* add complex trace api

* add complex sum api, test=develop

* modified en doc of complex sum and trace, test=develop

* modified doc and trace API, test=develop

* modified en doc of trace and sum, test=develop

* modified comment in complex kron API, test=develop

* OP Should Not Have Unused Input, test=develop

* add GetExpectedKernelType, test=develop

* add kron op and its python API, doc and unittests.
* add kron in paddle.complex

* Init complex number neural network, test=develop

* Improve doc writing, test=develop

* Fix elementwise add & sub, test=develop

* Fix elementwise mul act, test=develop

* a) add ut for complex variable; b) remove arg act in elementwise_ops. test=develop