Add support for v2.1.1

mc_openapi/assets/doml_meta_v2.1.1.yaml

mc_openapi/assets/doml_v2.1.1.ecore

mc_openapi/doml_mc/common_reqs.py

mc_openapi/doml_mc/intermediate_model/metamodel.py

mc_openapi/doml_mc/xmi_parser/special_parsers.py

tests/doml/v2.1.1/.project

tests/doml/v2.1.1/faas.doml

tests/doml/v2.1.1/faas.domlx

tests/doml/v2.1.1/iot_simple_app.doml

tests/doml/v2.1.1/iot_simple_app.domlx

tests/doml/v2.1.1/nginx-aws-ec2.doml

tests/doml/v2.1.1/nginx-aws-ec2.domlx

tests/doml/v2.1.1/nginx_func_req.doml

tests/doml/v2.1.1/nginx_func_req.domlx