No longer hide players who are dead. With models, a death animation should be used instead

Some changes requested by celeron55

Rename a lot of things in the code, and use better lua api function names

Minor code corrections

Bump protocol version up, since the models / animations / attachments code creates new client<->server messages

Send animations, bone overrides and attachments in entity initialization. Clients no longer have to be near an object when an animation or attachment is set to see the changes, and newly connected clients (or a client that simply renders the object for the first time) will get all of those settings. Therefore, the lua script no longer needs to run every X seconds either, just once per entity.

Finish fixing the material color code. But it won't work until MineTest has dynamic lighting... another day another feature.

Extra checks for the bone positioning / rotation code

Many checks and consistency improvements to the client attachment code

Make a separate function for checking if a client object is attached. A more in-depth change will be needed here to fix reading of invalid pointers

Use a different method of fetching the parent. Fixes the mass segmentation faults when rendering an attachment (some still happen though)

Major change to how attachments are handled. Fix the last segmentaton fault, which was due to the parent becoming invalid while being refreshed / removed which would bause the child to remain attached to nothing. Parents remove their children when being deleted themselves and add them back when re-added. Attachments are stored inside a 2D a vector which easily allows both a child to find their parent and a parent to find its children.

Remove attachment list entry when an object is being permanently removed. Also avoid duplicate entries in this list when re-attaching the same object

The "big code comments" can now go away. Client attachments almost work properly, and I know what else needs to be done

Fix some remaining issues with attachments, now they work. Tested with object->player and player->player attachments

Switch the license to be LGPLv2/later, with small parts still remaining as GPLv2/later, by agreement of major contributors