Extend the Autocomplete feature with extra options

[mistermark]

At the moment I'm overwriting the Autocomplete feature manually with some options that could be extended on top of the existing ones:

• position: absolute/fixed/relative
• top: enter a value or clear the value to allow positioning using CSS
• left: enter a value or clear the value to allow positioning using CSS

Also allow these options to be overwritten on /user level using a config.

[robhrt7]

Agree. Position should be configurable, when top/left coordinates should be calculated depending on input position.

This was originally Ilya's @cheshirsky (LP team) module, asking him directly could speed up the progress. Anyway, I will plan this in some of the nearest updates.