Check if menu is already loaded before getting via AJAX
Check if menu has been downloaded already before doing ajax request
Be more specific when overwriting content

Instead of doing:
	'html' => [...'main' => '']
Do:
	'remove' => 'main :not(menu)'
Merge from dev
Loop through json.attributes to set attributes by querySelectorAll
Added *.keys() method, returning Object.keys(this)
Handle json.remove in handleXHRjson using native functions
handleXHR now uses almost entirely native JavaScript