[#80051330] Change config API

- setEnvironment becomes loadConfiguration
- expose promise 'whenReady' that resolves once the configuration is loaded
- to migrate apps using koast.config.setEnvironment, simply change to
koast.config.loadConfiguration

When starting a koast application, two ways to do it:

koast.config.loadConfiguration()
koast.config.whenReady(function()
{
  // stuff that relies on configuration being loaded
});

or

koast.config.loadConfiguration(function(config)
{
  // stuff that relies on configuration being ready
});

- Removed unnessicary config files from koast/config folder