Update, reactivate and split Greek-various.xml

Hi,

The ruleset you created in https-everywhere has been disabled because some targets stopped working. Could you fix it and reactivate it please?

Also, to prevent this from happening in the future, could you split it in several rulesets, with only one domain in each?

https://github.com/EFForg/https-everywhere/blob/master/src/chrome/content/rules/Greek-various.xml