Remove unnecessary, update readme

• All info from wiki is moved to readme
• Fix Dockerfile so one doesn't need to set buildpack explicitly during deploy
• Arcgis decoding is removed

Separate django app and bot handlers logic

Before:

• tgbot handlers are messed with django tgbot app

After:

• tgbot is a separate folder, which contains logic only about bot, not about users, views, models and so on
• separated dispatcher and system_commands which are displayed in the main menu
• created new django app users

Some minor fixes

• postgresql url in .env_example
• freeze versions in requirements.txt
• fix typo: pooling -> polling
• dont broadcast message to users via Celery if DEBUG=True

Enhance

• using update.effective_user instead of self written if/else solution

Migrate to PositiveBigIntegerField and other minor fixes

1. Using PositiveBigIntegerField for user telegram ids
2. Add context: CallbackContext typing
3. Remove unused fields from User model
4. Add GetOrNoneManager. Example of using: user = User.objects.get_or_none(user_id=<some_id>)
5. Add AdminManager. You can select all admins via User.admins.all() instead of User.objects.filter(is_admin=True)

v2.0

New bot structure, native bot menu