feat(ui5-suggestion-item): add new component

[ilhan007]

An abstract item to serve as a suggestion item within the Input. Based on the suggestion item properties, the Input will display either a StandardListItem, or a GroupHeaderListItem within the suggestion popover.

FIXES: #1313

The usage becomes:

<ui5-input id="myInput2" show-suggestions >
        <ui5-suggestion-item group text="group 1"></ui5-suggestion-item>
	<ui5-suggestion-item text="Cozy"></ui5-suggestion-item>
	<ui5-suggestion-item text="Compact"></ui5-suggestion-item>
	<ui5-suggestion-item text="Condensed"></ui5-suggestion-item>
</ui5-input>

Although this is still compatible:

<ui5-input  show-suggestions >
	<ui5-li>Cozy</ui5-li>
	<ui5-li>Compact</ui5-li>
	<ui5-li>Condensed</ui5-li>
</ui5-input>

[vladitasev]

Everything works, tested on IE as well.

kitchen-scripts.js has not been modified to use the new item, but it's good to have one place to check for compatibility so let's keep it IMO