Final fixes and changes

[dimitar-st-atanasov]

1. Added more endpoints in teams and players routers:

• add_player_by_id_to_team (admin or director(owner of the team))
• remove_player_by_id_from_team (admin or director(owner of the team))
• edit_player (админ или директор(if player is not connected to an user), user(if user is connected to a player))

2. Uploaded the last version of MariaDB datascript into datascript.sql and all predefined tables into predefined.sql.
3. Wrote full description in readme.md together with @petar-georgievv and @yasen-sotirov
4. Uploaded a screenshot of the SQL diagram together with @petar-georgievv and @yasen-sotirov
5. Changed expiration time of token from 180 min to 30 min
6. Called send_email function when users verify their account so an email can be send to them