* Testing out some ideas for better error messages on AvgPool

* Add uncaught_exception() check to ConstructionAssertLogger dtor

* More general assertion class, not homed inside Node

* Minor formatting change

* NODE_ASSERT for type prop failure

* Produce lighter-weight DummyAssertionHandler when assertion succeeds

* New ctor for AssertionHelper that takes a single location arg; more const&-ness for the constructors

* Remove move constructor for AssertionHelper; fix broken test in assertion.cpp

* Miscellaneous improvements

* Templatized AssertionHelper so different exception classes can be used; implemented TYPE_CHECK_ASSERT around this
* Changed from a "stack" of locations to a single location (the stack was too complicated)
* Added "FAIL" classes/macros which do not take a condition

* Rename a helper function

* Cleanup, cruft removal

* Add test to make sure the assert helper has the lifetime we expect

* Missing includes