Create Tunneller and Create Digger setup

[Spatulade]

For association with Create Tunneller and Create Digger Keeper Spells, tidying of coloured icons #82. Setting up 'Create Tunneller' spell and setting up graphics. If inappropriate to bundle, let me know and I'll put it on the KeeperFX Workshop instead (although I currently think the spell casting cursors don't work with JSONs, but I might be wrong).

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Edit by @Loobinex

• Added Create Tunneller spell
• Reworked keeper powers to no longer need a specific player state
• Removed all non-needed power related player states
• Cost functions on keeper power configurable (non, digger, dwarf are the current options)
• New strings and old string fixes
• Power timebomb moved to new slot to make room for create tunneller

With this PR it is now easy to create new 'create creature' powers.