Add SonarCloud.io

[Ingvord]

SonarCube hosted on sonarcloud.io seems to be much better alternative(addition) to codacy.

Result of the analysis of this branch can be found here

[bourtemb]

When looking quickly through sonarcloud documentation (https://docs.sonarqube.org/display/PLUG/Building+on+Linux), it seems we must to run build-wrapper-linux-x86-64 before sonar-scanner for C++ projects.
I saw somewhere this could avoid some false positives.

There is a project referenced by https://github.com/SonarSource/sonarcloud_examples with a C++ example where they run build-wrapper-linux-x86-64 before executing sonar-scanner: https://github.com/SonarSource/sq-com_example_c-sqscanner-travis/blob/master/.travis.yml

[Ingvord]

@bourtemb , yes, you are absolutely right! That would be further improvement. We just need to figure out how to integrate build-wrapper into our dockers (which BTW would be nice to replace with native Travis images if possible). Anyway at this point it is already a good result, and I like the result of the analysis.

[bourtemb]

I understand...
Can we add a sonarcloud badge to the README too?

[Ingvord]

@bourtemb , sure! Once we merge it and run analysis on the tango-9-lts branch we can add sonar metrics to readme, like in JTango's readme

[Ingvord]

@bourtemb , build-wrapper is added in fbc9707

Interesting that with build-wrapper sonar found 158 new bugs and 30 vulnerabilities and coverage has dropped from 49 to 33%. Anyway I feel we have now much better picture