ComboBox Component about belle

[jpuri]

Autocomplete has been renamed to combobox and is largely completed. But there are still a few points I was to note here so that we do not miss:

1. Right now we do not have a hover style for caret but will be probably a good thing to add.
2. Add option for highlighting matching text for combobox input in option - this looks good and we should have.
3. Right now when you navigate through options using keyboard their value is temporarily copied to combobox input. I had put it there coz many combobox out there I found have this feature. But it at times look misleading giving impression to user that value has been changed and is also error prone. We can think about removing it.

[nikgraf]

Interesting at point 3. Intuitive I would have expected the value only to change after the user selected it (space or enter)

[nikgraf]

@jpuri I will close it. We can bring them up as separate issues. I can do that.