ClipboardTool uses deprecated hs.mouse.getAbsolutePosition; right-click menu has errors

I noticed a few minor ClipboardTool bugs when right-clicking an item in the clipboard list. I've fixed these so I'll fork and raise a PR.

1. The console to show a deprecation warning for using `hs.mouse.getAbsolutePosition` instead of `hs.mouse.absolutePosition`.

2. Selecting one of the special paste actions throws an error about a type mismatch. `"entry"` should be `"entry.content"`.
```
ERROR: LuaSkin: hs.menubar:setClickCallback() callback error: ...hammerspoon/Spoons/ClipboardTool.spoon/init.lua:241: attempt to concatenate a table value (local 'entry')
```

3. Using the special paste actions writes the output into ClipboardTool's filter box rather than prevFocusedWindow.