[EquipViewer] Add draggable option for UI elements

[aragan]

Add draggable option for UI elements

[RubenatorX]

It's helpful if you talk to an addon Author before submitting a PR, but I'll let you know what I was planning and what I need changed in order to accept it.
Also, in the future please always include the name of the addon/thing you're changing in square braces at the start of your PR (in this case) [EquipViewer] (I have edited the title as such).

1. You wrote an entire function, position_all_ui_elements, that is basically a non-destructive duplication of setup_ui. Instead, should add an optional flag to setup_ui to make it nondestructive, and call it with the flag.
2. I won't accept draggable as being a save-able setting. it should be a temporary addon state, toggleable with a command move instead (instead of drag/draggable), and only save the config after it is toggled off. Also should not have an off/on command option. Relevant instructions and feedback should be conveyed to the user when this is toggled.