major rework of ythdd.py, new method for setting config in ythdd_globals.py

- slightly modified config, api keys now have the value "CHANGEME"
- requirements.txt has new dependency, flask apscheduler
- ythdd.py has been reworked, support for argument parsing has been added, code is now split into functions
- ythdd_api_v1.py features real uptime as well
- ythdd_db.py is no longer dependent on ythdd_globals.py
- ythdd_globals.py has a method for setting config and getting it from configfile variable

config.default.toml

@@ -4,9 +4,8 @@ video_storage_directory_path = "/path/to/videos/" # Path to video vault.
 is_proxied = false
 
 [api]
-# Leave empty to autogenerate api keys every launch (secure).
-api_key = ""
-api_key_admin = ""
+api_key = "" # Leave empty API key for public access to non-sensitive backend
+api_key_admin = "CHANGEME" # Empty *admin* API key will autogenerate a random one every launch.
 
 [extractor]
 user-agent = "" # leave empty for default