Implement "ignore envvar" feature for Flask framework

[rafaelhenrique]

Now this project support some "default ignored" envvars for Django Framework. There is a possibility to implement this same feature in the Flask framework.

We need an new file called "flask_utills.py" (like django_utils.py) , and implement a new functions like these:

• is_django_project: This function check if this is an django project;
• get_base_envvars: This function get a base envvars used in django (ignoring a custom envvars).

For flask i suggest these names:

• is_flask_project: This function check if this is an flask project;
• get_base_envvars: This function get a base envvars used in flask (ignoring a custom envvars).