Apa/hetero no legacy

[ilya-lavrenov]

Resolved merge conflicts for #2996

[myshevts]

Upon rebasing my private new fetaure branch to the latest master (that includes the MULTI switching to the ngraph only) , I have realized that "MULTI:CPU,GPU" now doesn't accept some old IR (ver4 that the MLS team is actively playing with) and this is fine, but CPU and GPU alone are still reading fine this old IR. This is a little bit of inconsistency. Generally the ngraph (and/or v10 IR ver) check should be done in some common place, maybe even IR parsing. Fyi, @ilya-lavrenov and @slyalin

[ilya-lavrenov]

@myshevts just remove inference_engine_ir_v7_reader from your build artifacts and you will get an exception you expected.
inference_engine_ir_v7_reader is used only for our tests (since still a lot of them are based on IR v7 and earlier), but it's not a part of OpenVINO release package.