Surge improvements

This adds two new settings (both disabled by default) which affect the Surge button.

The first setting SurgePlusPrompt prompts for additional healing and adds it to their base surge.  This is extremely useful if you have a healer who almost always adds something to the player's surge value.

The second is AutoSurge, which pops up a Yes/No messagebox with how much they will be healed, and warns you if they are out of surges (but gives you the option to continue anyways).  If you click yes, it heals them and marks a surge as used.  This works well for me, because I am constantly forgetting to keep track of surge usages.