clearer what template argument is being specified. #702

  Now we use the folder of the header file where the type is defined as the root context.
  Types declared in header files located in child sub-folders will also be exported.
* Code generator now complies with the new coding standard.
* Fix contract annotations.
* Fix simpledb / Use the generated functions to deserialize/dump messages.
* Add optional flag to eoscpp generate-abi command to also generate serialization helper functions for the types defined in the ABI file.
* Fix abi_tests.

This commit will likely break the currency and/or exchange contracts.

- implement a large part of example exchange contract

TODO: replace Makefile with CMakeLists