eslint-bridge should return specific code when linter is not initialized

[saberduck]

SonarLint in Visual Studio sometimes needs to recover from exceptional conditions - out of memory, etc.. They need to able to detect when calling /init-linter is necessary. Currently, if /init-linter is not called before analysis, we throw generic exception. We should change this to return specific error code which can be interpreted on SonarLint side.