* cleanup pass registration code.

* Replace explicit code to do passes with pass_manager passes

* make external function work with const types internally, it should not change the graph

add tensor buffer size unit test

fix warnings when building mkldnn test

get tensor is_output set. Add Manager state and Function to pass manager

use pass manager internal state

* Done to achieve goal of having our #include directives all start
  with `"ngraph/`, like LLVM does.

Add memory layout and liveness passes.