Fix issue with use-config-ini option. Implement a better way to add variable values in templates.

Fix some issues with --use-config-ini parameter. The generated project was missing some code to work with the config.ini file.

Implement a better way for adding variables values in the templates. Now it's possible add variables in templates through a json file. Current parameters just return true or null, and that's why the current implementation doesn't support other values, but this can be implemented in a very easy way. Not sure if json is the best here, any other format could be used.

Also refactored some code, specially the code generating project files. Now all goes through the function ProjectBuilder::generateFile, which checks if the file requires some modifications.