Added keyboard shortcuts for faster navigation

Added keyboard shortcuts for pull-down menu item and most used buttons (searchHash, download, close)
Download button downloads first in search list if user didn't select any
Automatic searchHash on first load
Plugin window closes now straight after download

IDK if the autoclose and autosearch are useful, but I included them still. mess_no_selection is probably not the best way to respond in a situation where "no selection has been made and the search list is empty"