Add two new slapps to support wearing contents of folders - Add and Remove

[kylelinden]

What does this feature/enhancement do? Why is it needed?

Add two new slapps -- one to add the contents of a folder to the avatar, and one to remove the contents of a folder.

Test Plan

Older QA SLapp test page (untrusted)
https://sl-viewer-media-system.s3-us-west-2.amazonaws.com/html/slappr.html#

Need to add a new viewer-based menu or floater to test SLapps from a Trusted source.

[maxim-productengine]

/wear_folder slapp which is used in 'Complete avatars' floater only allows wearing Library folder.
Should we restrict the new 'Add' command to Library folders too? Keep in mind that, there may be several folders with the same name in the user's inventory.
(wear_folder is restricted only when using folder name. So, its currently possible to use folder id(if you know it) instead, to wear non-Library folder too. So, I assume I should do the same for the new command)

And the second question is related to 'Remove' command. It's easy to do if 'folder id' is provided. But if we'll try to do it using 'folder name' param, we may need to iterate through all the folders with that particular name. So, do we still want to allow 'Remove content' by folder name?

[akleshchev]

Wearing or removing by name is not practical.
Inventory is not warrantied to not have dupplicate names. And there might be two different outfits, one unmodified in library and one modified in invenory. Library copies folder to inventory so we can no longer remove it by name 'from library'.

[maxim-productengine]

Agree, wearing/adding by name from Library is OK, but not from user's Inventory.

[DarlCat]

It'd be really nice for individual use if we could address folders by UUID outside of the library; just two cents from a resident. Potential for abuse there is basically zero imo, and would be greatly appreciated as an extension of the functionality.