C/C++ Integration tests

[vaind]

Create a full integration test - it should contain a schema and "project files" for each langauge (cmakelists, main), excluding the generated code.

• The test should generate code, compile and execute the compiled code, expecting 0 return value.
• Catch2 should be used.
• Actual code should do database operations in a temporary directory and clean up after itself.

Follow up of #1 Depends on #2