RAPyDo 0.6.7 (#25)

* Upgrade to RAPyDo 0.6.7

* Upgraded flask extentions

* Forcing oauthlib==2.1.0 due to incompatibility with requests-oauthlib

* Forcing requests-oauthlib==1.1.0

* Forcing PyMySQL==3.13

* Fix to always checkout the branch, also when testing the master branch

* Update LICENSE

* Added checks for missing parameters in url schemas

* Removed debug print

* Upgraded Flask to 1.1.1
 
* Dropped Python 3.4 support

* Introduced Celery beat app

* Celery beat scheduler is now based on MongoScheduler

* Tests extended to admin users endpoint

* Dropped support images building during init

* Setting coveralls env

* Testing coveralls outside the script

* Fix to merge coverage from python 3.6

* First integration of Flask-Migrate

* Improved error reporting in case of errors when loading an extention

* Enabled compare_type in Flask-Migrate to let Alembic to detect type changes in columns

* Removed fill_custom_payload method in authentication

* Roles are now provided as dict instead of list to report both key and description

* Black formatting fixes

* Check on enabled services

* Removing obsolete test resource

* Default values for celery crontab_tasks

* Bug fix plain body in sending credentials email

* Bug fix to manage strange urls like HEAD /?952

* BUG fix loading core endpoint on non-canonical http-api installations

* Fix to avoid hardcoded upload folder