Finish broadcast type propagation, add tests.

Add eigen support

add eigen as external project.
add very simple eigen unit test to test building/linking

Fix/sanitize type comparisons, add test

* Cleaned up the CMakeLists.txt to properly do the include paths and fixed the install targets.
Also cleaned up the header files located in sub directories.
* Added a simple C++ example with Makefile.
* UPdated the readme with TF usage instructions.

De-use and cleanup op names.

Cyphers/names

topological sort working with unit test

Bob/relax requirements

Disable infinite recursion in ScalarConstant::node_id()

Use direct implementation of is_parameter, is_op

Add topological sort and viualization classes

Cyphers/literal

A few using types for things that aren't class-worthy to help with {} initializers