Added option to buff health potions to original 1.5 amount

This was NOT requested by an admin, but a player. I am simply adding this on the off chance it is decided we want to do this later, the code to do so is finished. 

Code taken from [here](http://www.reddit.com/r/MineZ/comments/1hx9fc/162_potions_message_to_the_developers/cayuthd), and suggested by IDANUB [here](https://nerd.nu/forum/index.php?/topic/588-vanilla-pvp-is-broken-in-16/#entry4614). 

If you choose to include it, please set the config to false on survival until it is decided that this is needed by one of the s-admins/the community/whoever decides these things. Thanks!