Skip generation for invalid stubs

[DenTray]

At the moment if there is invalid stub name in the package config, generation will be failed with the next error

It's not clear for package users what exactly brake the process.

We need to make the following:

1. Throw human readable error Generation of $classType has been skiped cause the view $viewName from the config $configName is not exists. Please check that config has the correct view name value.
2. Class with incorrect stub name should not be generated
3. Other classes should be generated (if they not related to skippable class)