Attack Sprite ToHit is wrong after deleting an attack

[pakfront]

Environment

49.14

Description

The AttackSprite tooltip will always show the To Hit number for attacks as Impossible if you delete an existing attack with Backspace. This is because the ToHit .getValue() for an attack changes to Impossible after a new attack is added. Reason behind this is unknown by me, and it may be working as intend but is also causing UI issues elsewhere. Possible fix, if this is intended, is to cache the ToHit value somehow.
In addition, it would be good to change BoardView.attackSprites from ArrayList to HashMap as there is a lot of iterating looking for matches, and rebuilding which defeats caching.
There are also a few other minor issues with AttackSprite that could be cleaned up here, and a chunk of the text generation code moved to a central, static area so it can be share with other UI.