DicConfigLoader: better error handling

[matuszeman]

Story

As developer, I want to know clearly that I passed invalid object into loadConfig method.

Current behaviour

We get unclear error what might went wrong when non JSON object is passed into loadConfig method:

/src/dic-config-loader.js:45
_.each(config.options, (opts, service) => {
TypeError: Cannot read property 'options' of undefined

Suggested implementation

loadConfig validation should be improved