Icon|Dropdown: components use an icon as indicator

[layershifter]

Feature Request

#721 introduced the Indicator component, it resolved issues with arrows. However, we have issues with clearIndicator on Dropdown (#885) and Input, it relies on the close icon that can be undefined in the theme.

Proposed solution

1. Add base icons, may be even inside the indicator component
2. Find the correct unicode char for cross/close action and use it in Indicator component