Give more descriptive labels to flags

config/optional/flag.flag.subscribe_node.yml

config/optional/flag.flag.subscribe_og.yml

config/optional/flag.flag.subscribe_term.yml

config/optional/flag.flag.subscribe_user.yml

..._subscribe_email/config/optional/flag.flag.email_node.yml

...ge_subscribe_email/config/optional/flag.flag.email_og.yml

..._subscribe_email/config/optional/flag.flag.email_term.yml

..._subscribe_email/config/optional/flag.flag.email_user.yml