[SUGGESTION] Replace copy tool with menu tool copying

[thecraftianman]

Short Description

The existing copy tool should be removed and replaced with a copy ability in the menu tool instead for much more convenient editing of values. This can simply use the reload button while in the entity spawning/updating mode since that button is currently unused there. This change requires an overhaul of how both entity and menu client data are handled to allow for proper two-way communication (related to #230), though some partial progress has been made on this front already.