Patch notes 9.73

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Update 9/23/2019 ~~ Besti 9.73p
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==Core Updates==
Modified the Extra Friends system to support changing to your custom friends rather than the pre-assigned ones.
Wrote the UI systems for custom friends in the Extra Friends situations in the scenes where this is possible.
Wrote most of the friend swap code involved in changing the Extra Friends into custom friends. I disabled it for this build and replaced the functionality with a message in the error log indicating what it would have done if the code was ready. The correct file is loaded in and processed, but I need to write the programs to handle eye-changes, body color changes and mane/tail assignment. The removal process is already done but disabled in this release. I estimate ~6 hours of work remains on that for it to be functional so I should be able to finish it for 9.74.

==Bug Fixes==
Altered the elbow-bend influencer in the laying position to improve avatar function in the laying-down position. In 2D mode the default head/arm rotation was clipping through the floor.