Extend reference model API with eager operator execution entrypoints

- Adds a script to generate operators.h and operators.cc
- Adds jinja2 templates for generating operators.h and operators.cc
- Adds unit tests for a subset of the operators generated
- Includes the TOSA specification as a submodule
- Adds supporting C++ and header files

Signed-off-by: Grant Watson <grant.watson@arm.com>
Change-Id: I5b60db4c56113110d8e75fe1152525d258233f9c
diff --git a/.gitmodules b/.gitmodules
index 87ce1ef..5ed5edb 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -10,3 +10,6 @@
 [submodule "thirdparty/doctest"]
 	path = thirdparty/doctest
 	url = https://github.com/doctest/doctest.git
+[submodule "thirdparty/specification"]
+	path = thirdparty/specification
+	url = https://review.mlplatform.org/tosa/specification