Added external_port to config.yml

Added external_port to config.yml Configuration
- Changed update check on first run to exclude notes (since curl might not be installed)
- external_port will be set to 443 if https_only = true, else < blank > (assuming use of reverse proxy with https.)
- Set default domain to invidio.us since option now is blank in config. (blank domain doesn't work on local instance)
- Created IRC Channel on Freenode.net/#InvidiousUpdater