feat: add update command to manage.py

[bbmt-bbmt]

This update command does:

• git checkout master && git pull
• git checkout to the last version
• lauch pip3 install --upgrade -r requirements.txt
• manage.py migrate
• manage.py collectstatic
• manage.py compilemessages

TODO:

• [ ] documentation

[fallen]

Looks good to me! Do you want me to wait for some documentation update before merging?

[bbmt-bbmt]

I would have liked to write some documentation but my English is too bad. You can merge, thanks :-)

[fallen]

No problem I'll do it :) Merging, thanks a lot!