Patch 4.1.0/API changes

== Breaking changes ==
* COMBAT_LOG_EVENT and COMBAT_LOG_EVENT_UNFILTERED have a new third parameter, hideCaster.
* Addons are now required to register the prefixes they want to receive messages for using .
== API changes ==
* REMOVED / ; worgen transformation is now treated entirely as a spell.
* REMOVED along with actual pet happiness.
* REMOVED 
* NEW calendar extensions
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* NEW Looking For Guild / Guild Recruitment API
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* NEW Looking for Group Call To Arms (role shortage) API
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* NEW Guild Challenges API
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* NEW Opt-in Addon Communication API
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== Event changes ==
* COMBAT_LOG_EVENT and COMBAT_LOG_EVENT_UNFILTERED have a new third parameter, shifting existing parameters to the right.
* REMOVED END_REFUND, items no longer become unrefundable due to enchanting, etc.
* REMOVED HONOR_CURRENCY_UPDATE, honor now treated as ordinary currency
* REMOVED INSPECT_TALENT_READY, talent information available by default.
* REMOVED KNOWN_CURRENCY_TYPES_UPDATE